Royal Society (Great Britain).

The Philosophical transactions of the Royal society of London, from their commencement in 1665, in the year 1800 (Volume 8) online

. (page 21 of 85)
Online LibraryRoyal Society (Great Britain)The Philosophical transactions of the Royal society of London, from their commencement in 1665, in the year 1800 (Volume 8) → online text (page 21 of 85)
Font size
QR-code for this ebook


F.R.S. fVith a Remark, by the Secretary, Dr. Mortimer. N''447, p. 153.

Mr. Brown presented a creature, whose name he could not learn from any
books or persons. He brought it from a pond on Bexby Common, where great
numbers had been observed for 5 weeks before. The pond was quite dry the
24th of June, but on its being filled with the great thunder-shower on the 25th,
within two days the pond was observed to swarm with them. And it was
thought observable, that there is no duct or channel that could convey them
from any adjacent place.

Here E, fig. 6, pi. 6, represents this insect. Its legs are very extraordinary.
Dr. Mortimer counted 42 on a side, in one of those found in Kent ; the 20
next the head are nearly of a size, but then they grow gradually smaller and
smaller towards the tail. He took out one of the larger ones of the left side
of the chest ; the foot consists of 5 flat membranous claws, with a stiffs rib
along their middle, and beset with hairs on the edges, like those of crabs ; on
the lower side of the leg hangs an oval bag, and beyond that grows a large thin
membrane, which can be extended by a bony rib that runs across it ; this mem-
brane and the whole foot, is convex on the side next the head, and concave on
that next the tail ; the thigh, or first joint of the leg, is webbed on each side ;
so that the whole structure of the legs seems to show that they are rather de-
signed for swimming with, than walking. The leg represented at e, was drawn,
when the insect lay on its back, as at b. Many parts of this insect, though no
larger than the figures, have some resemblance to those of the Molucca crab.

/in Account and Abrtract of the Meteorological Diaries for the Years 1729 and
1730. By Geo. Hadley, Esq. F.R.S. N" 447, p. 154.

The diary kept by Mr. Hauksbee, by order of the Society, at their house in
Crane-Court, consists of observations of the barometrical heights twice a day,
i. e. morning and evening, in inches, decimals and centesimals ; the thermo-
meter likewise, in its proper graduations, and the weather, with the hour of each
observation. The winds are omitted. The depth of rain is set down several
times for the most part in each month, the sum of which is to be divided by
10, the funnel which catches the rain being so much larger in surface, than that
of the vessel which receives the rain from it.

Y 2



l64 I'HILOSOPHICAL TRANSACTIONS. [aNNO 1738.

That from Southwick, near Oundle, in Northamptonshire, by George Lynne,
Esq. contains the height of the barometer once a day, and the winds, the
steadiness and strength of which are likewise marked with proper marks and
figures. Observation is made of the upper and under currents of the air, when
it so happened. The thermometer is marked twice a day; the weather often,
both by day and night ; the rain from time to time, and the quantity of each
particular shower often set down by itself, with some other miscellaneous obser-
vations, as haloes, thunder-storms, and sudden changes of wind, &c. He re-
marks that his thermometer is placed in an out-house exposed to the air, but
screened from the sun, which is a proper precaution in using that instrument.
The remarkable rises and falls of the Mercury are also marked with proper
marks ; which method would be useful in the other columns also, for com-
parison of diaries, if some certain rule were agreed 'on.

That from Kent, l6 miles south east from London, gives an account of the
barometer once a day, sometimes twice or thrice, with the hour of each obser-
vation, and the winds, weather, and rain, the proportion of which for every
day, is given at the end of each month. There is also a separate column for
the height of the clouds, which is divided into three orders ; and where there
are two orders at a time, they are both noted ; as also when any of them move
with different velocities or directions, which he supposes to be commonly a
sign of change of the wind : but he does not inform us by what method he de-
termined their heights or velocities. The reigning wind, and general strength
of it, is noted at the end of each month ; the eclipses also, and the times of
the new moons ; which he observes make it appear, that the notion of the
change of weather depending on the age of the moon, is without any ground :
with other miscellaneous observations ; as the aurora borealis, fruitfulness or
sterility of the season. He had no thermometer.

That from Hudicksvall in Sweden, by M. Olave Broman, shows the height
of the barometer, sometimes once, sometimes twice or thrice a day, o. s. in
English measure, with the winds, and the strength of them, and the weather.
There is also to the diary 1 72Q, annexed an account of the height of the sea-
water for every day, which varies in the whole about 1 inches, and is sometimes
interrupted by floods from rain. This probably relates to the tides in the gulph
of Bothnia. There is no thermometer, nor the quantity of rain set down.

That from Risinge, in Ostrogothia, in Sweden, by Sueno Laurelius, pastor
and provost, gives the height of the barometer for the most part 3 times, some-
times 5 times a day, with the hour of the observations, o. s. in English mea-
sure. He refers for the descriptions of his barometer and thermometer to the



VOL. XL.} PHILOSOPHICAL TRANSACTIONS. I65

diary 1727. The winds, with the degree of their strength, weather, and depth
of rain, are also set down.

In that from Upsai in Sweden, by Mr. Andrew Celsius, Astr. P. R. and F.R.S.
observations are made 3 times a day, of the barometer and thermometer, both
which instruments were made by Mr. Hauksbee; the winds, with their strength,
and the weather, and depth of rain, from time to time.

That from Svenaker in Sweden, near Trollhetta, by Torstanus Wassenius,
V. D. M. &c. contains the height of the barometer twice a day, sometimes 3
times, o. s. in Swedish feet and inches and decimals, which being supposed to
be in proportion to English as 974.375 to 1000, the mean heights are reduced
in the tables into that measure. The winds also, with their strength, are noted,
and the weather. There is no thermometer. Notice is taken on thunder
storms, and other meteors.

That from Lunden in Sweden, by Mr. Conrad Quensel, Math. Prof, in
Acad. Carolina, contains observations of the barometer twice a day, o. s. in
English inches and decimals, and 4ths of them ; the winds, with their strength,
and the weather. The thermometer is Florentine, and therefore the observa-
tions not inserted in the table.

That from Bygdea in Sweden, by Mr. John Telinus, pasor there, has obser-
vations of the barometer twice a day, morning and evening, o. s. in English
inches and decimals ; the winds, with their strength, and weather. The two
last months are wanting. There is no thermometer.

That from Betna in Sudermanland, by Mr. And. Geringius, pastor and pro
vost, has observations of the barometer thrice a day, except in the first part of
January, o. s. in English inches and decimals ; the winds, with their strength,
and the weather, with other meteorological observations, and on the seasons,
as to fruitfulness and sterility, &c. The aurora borealis is frequently mentioned.
The thermometer is peculiarly graduated, and so could not be inserted. There
is a column for rain.

From Wittemberg in Saxony, there are two diaries communicated, one from
Mr. Mat. Hasius, Math. Prof, the other from Mr. J. Fred. Weidler, LL. B. and
Math. Prof. Primar. That by Mr. Hasius has the height of the barometer
several times a day, sometimes 4 or 5 times, o. s. in English inches and deci-
mals, and the parts of these in vulgar fractions, but are reduced to decimals in
the tables. He used two barometers and thermometers. Those marked i, are
Mr. Hauksbee's, those marked ii, Florentine. The coldest day he ever ob-
served, was February the 5th 1726. It contains also the winds, with their
strength, and weather. Mr. Weidler gives the height of the barometer 3 times
a day, n. s. in Paris inches and lines, and the parts of these in vulgar fractions;



|66 PHILOSOPHICAL THANSACTIONS. [aNNO 1738.

the winds also, with their strength, and the weather, and quantity of rain, in
cubes and lines, but at the end of each quarter the depth is given in Paris inches
and lines. The thermometer is Mr. Hauksbee's. There are some astronomi-
cal observations of eclipses, &c. He takes notice, that an occultation of Venus
by the moon, observed with a telescope of 18 feet, may serve to prove the
moon to have an atmosphere ; for being then in the quadrature with the sun,
the planet appeared to lose its cusps, and become oval, when it came near the
moon.

That from Padua, by the Marquis Poleni, shows the height of the barometer
once a day, o. s. in English inches and decimals ; the winds, and sometimes
their strength, and weather. The depth of rain is given both for the old
and new style.

That from Bengal, by Mr. Bellamy, preacher to the factory, has the height
of the thermometer twice a day, morning and evening ; the winds, with their
strength, and the weather, for the year 1730. The medium of the thermo-
meter is taken from both the evening and morning heights, the difference there
being very great in proportion between morning and evening.

That from Boston in New-England, by Paul Dudley, Esq. F. R. S. shows
the weather 3 times a day, and wind once or twice. No barometer or ther-
mometer.

The Abo observations for the year 1730, by Mr. D. Sporing, show the height
of the barometer twifce a day, in Swedish inches and decimals, but the mean
heights are reduced to English in the tables. They show also the winds and
weather, and in the last column the aurora boreales, which are frequent in most
months of the year.

That from Naples, by Cyrillus, shows the height of the thermometer, which
is Mr. Hauksbee's, once a day. The winds, with their strength, and weather,
and depth of rain in Neapolitan measures, 23 of which make a London inch.
The barometrical heights he has not set down, because he found them not to
agree with those of former years, which made him suspect his instrument to be
out of order ; but as it appears he had removed his habitation, it might be
owing to its being situated higher or lower than the former. An eruption of
Vesuvius happening, an account is given of it, and of damage done by light-
ning, and also of the seasons, as to fruitfulness and healthiness.

First, he observed on the barometrical tables of these two years, that they con-
firm former remarks made by Dr. Derham and others, of the consent of the
barometers in places at a good distance from each other. Not only the monthly
mean heights agree in the three diaries of these two years here in England, but
also the greatest ascent and descent of the mercury happen commonly on the



VOL. XL.] PHILOSOPHICAL TRANSACTIONS. I67

same day, and the barometers have been found to agree in their motions to an
liour, so far asunder as Townly in Lancashire, and Greenwich near London,
which is near l6o miles, though that might be partly accidental. The baro-
meter at Crane-Court and Southwick, distant about 55 miles, being compared,
seem very seldom to vary from their mean difference above -fV and 4- each way ;
at Southwick and Kent something more. From whence it might be expected,
that the weather should be much the same in all these places ; which yet seems
not to agree with accounts in some years from different parts in this island, not
very far distant : and Mr. Hadley has observed sometimes clouds to lie in one
part of the horizon for a great part of a day, which have discharged a large
quantity of rain in places not far off, while the place, where he has been, has
all the while enjoyed fair weather, and vice versa. Whence it appears, that the
barometrical alterations of the air extend farther than their effects, as to the
production of rain, at those times. Comparing the diaries of Crane-Court and
Upsal, he finds the barometers vary from their mean difference an inch and half
each way; Crane-Court and Padua as much, or more, and often go a pace quite
contrary ways at the same time, and their monthly differences are also very
variable, so that their agreement at any time seems to be but accidental.

Secondly, he observes, that the descents of the mercury below the mean
heights of each place, taken in this way of Dr. Jurin's, are generally much
greater than the ascents of it above; and there are also other extraordinary de-
scents of the mercury in every year, of the same kind. The reason seems to
be, because the expansion of the air, by which it becomes lighter in some one
place, being the original of the alterations in the atmosphere, its effects by
condensation or accumulation of the air, in the places round about, will be more
dispersed, and therefore less sensible.

Thirdly, the variation or range is greater the farther north, as has been
heretofore observed, and appears in these tables; and likewise it is greater ge-
nerally in the winter than summer months. The sum of the motion of the
mercury upwards and downwards, taken from the Berlin wandering line, with
a pair of compasses, in the year 1726, amounts to about 7^ inches, which gives
54^ for a month, and about 0.21 for each day. But the barometer is by much
most steady in the summer.

4thly, The mean height of the barometer has already been applied to deter-
mine the respective heights of places, and also the absolute height above the
surface of the sea. Dr. Scheuchzer, in his Tables published in the Transac-
tions of this Society, N° 405, 4o6, supposes, from Mr. Marriot, the mean
height at the surface of the sea to be 28" l'" Paris measure, which reduced to
English, gives 29 inches, .993. This agrees very well with a Diary commu-



l68 PHILOSOPHICAL TRANSACTIONS. [aNNO 1738.

nieated to the Society, containing 10 months of the year 1723, and Jan. 1724;
the author of which found by experiment, that in the place where his barometer
was kept, the Mercury stood y^ and -i^ higher than at the surface of the sea,
which was not far from his habitation. The mean height of the barometer for
those 10 months (leaving out the January following, which seems to be a very
irregular month) is 29.825, to which adding -jV 4-, it will give the mean height
at the surface of the sea 29.975 ; so the difference between these is only, 018,
and therefore probably may be near the truth, but may hereafter be more
exactly determined by experiments. Then allowing about 90 feet, or rather
less, for each 10th of an inch in height of the Mercury in smaller altitudes, or
in greater according to the tables calculated for that purpose, by Dr. Scheuch-
zer and Dr. Nettleton, and published in the Trans. N° 388, you will have the
height of each place pretty nearly, provided the observations be carefully made,
and continued for a sufficient time ; for the yearly mean heights, in one of the
places in these tables, appear to differ near -j^ of an inch in these two years ;
and in most of them, the last of these two years exceeds the first, two or
three hundredths: the barometer also ought not to be removed to a lower or
higher place.

The thermometers agree, especially as to the hottest days in the year, more
than might be expected from places at such a distance.

The winds are of so uncertain and variable a nature, that they require a
more than ordinary care and diligence in making the observations, and a
great length of time, and comparison of a vast number of them, before any
thing can be deduced more than is commonly known; and therefore he only
gives this hint, that if the observers would take particular notice, in great
storms, of the time when the Mercury first begins to rise, whether before, or
after, or in the very height of it, it might be a direction to judge when an
abatement or increase of it might be expected, if any regular order should be
found therein, which might be serviceable on some occasions. But if any
attempt should be made to lay down any thing certain concerning the rise and
progress of the variable winds, it will appear, by considering the cause of the
trade-winds, that for the same cause the motion of the air will not be naturally
in a great circle, for any great space, on the surface of the earth any-where,
unless in the equator itself, but in some other line; and, in general, all winds,
as they come nearer the equator, will become more and more easterly, and
as they recede from it, more and more westerly, unless some other causes
intervene.



VOL. XL.] PHILOSOPHICAL TRANSACTIONS. iQg

A Collection of the Observations of the Solar Eclipse, Feb. 18, 1736-7, sent to
the Royal Society. N° 447, p. 175.

1. Observed in Fleet-street, London, by Mr. Geo. Graham, F.R.S. p. J 75.

Apparent Time.

At 2^ lb"" 9' P. M. a small impression appeared on the sun's limb; he judged
the beginning to have been about 5 or 6 seconds sooner.

A cloud covered the upper limb, and prevented a sight of the ending.

Between 12 and 1 o'clock, he measured the diameter of the sun with a micro-
meter. At the time of the greatest obscuration, the lucid part of the sun's
diameter was equal to 392 such parts, as his whole diameter contained 2188.

By a transit of the sun at noon, and of Sirius at night, which, compared
with preceding ones, he found his clock went too fast for mean solar time,
about one second in a day.

2. The same Eclipse observed at the Royal Observatory at Greenwich, in
Company with Dr. Edm. Halley. By Dr. J. Bevis, p. 176.

Apparent Time.
At 2'' 25"" 39' P. M. the beginning.

5 3 29 the end.

At the end, the sun's limb appeared somewhat tremulous, and a small thin
cloud came over it. Dr. Bevis judged the time might be relied on to 2 or 3
seconds.

3. At Edinburgh, by Colin Maclaurin, F.R.S. p. 177.

In the history of eclipses collected by Ricciolus, there are very few said to
be annular; and of these, some have been controverted, as that seen by Cla-
vius at Rome, April 9, 156/ ; and that seen by Jessenius at Torgaw in Misnia,
Feb. 25, 1598; which are both disputed by Kepler. Some astronomers, an-
cient and modern, have been of opinion, that no eclipse can be annular ; and
since such seem to have been rarely observed, and Mr. Maclaurin has not met
with a particular description of any of them, he gives as full an account of
this eclipse as he can collect from the observations that were made at Edin-
burgh, and those communicated to him from the country.

During the eclipse the sky was generally favourable in the southern parts of
Scotland; and though there were great showers of snow in the north, they had
sometimes a view of it. There was something very entertaining in the annular
appearance, a phenomenon that was equally new to all who saw it.

VOL. VIII. Z



170 PHILOSOPHICAL TRANSACTIONS. [aNNO 1738,

A little before the annulus was complete, a remarkable point or speck of
pale light appeared near the middle of the part of the moon's circumference,
that was not yet cpme upon the sun's disk ; and a gleam of light, more faint
than this point, seemed to be extended from it to each horn : Mr. M. did not
mark the precise lime when he first perceived this light, but is satisfied that it
could hardly be less than -J- of a minute before the annular appearance began.
Mr. Short, who was in another chamber at some distance, and made use of
a larger telescope, said that he saw it 20 seconds before the annulus was com-
pleted. He was surprised with this light at first, and did not immediately re-
collect that it proceeded probably from the same crown that was seen about
the moon in a total eclipse of the sun at Naples in l605 ; and was observed
by many in different parts of Europe in the three late total eclipses, of 1 706,
1715, and 1724.

Most of those who observed the eclipse with telescopes, mention in their
letters, that as the annulus was forming, they perceived the light to break in
several irregular spots near the point of contact, and that the moon's limb
seemed to be indented there. Some express themselves as if those irregular
parts had appeared to them in a kind of motion. Such appearances of a tre-
mulous motion, in certain periods of solar eclipses, are mentioned by Hevelius
and others.

The annulus appeared to the eye to be central for some time, but in the te-
lescope it was always broader towards the south-east, than towards the north-
west part of the sun's disk. The breadth appeared much greater to the naked
eye, than could have been expected from the difference of the semidiameters
of the sun and moon. This was so remarkable, that such a phenomenon must
have confirmed those astronomers in their opinion, who imagined that the dia-
meter of the moon is contracted in her conjunctions with the sun. This ap-
pearance probably proceeded chiefly from the light's encroaching on the shade,
as is usual; but whatever was the cause, every body seemed surprized that the
moon appeared so small on the disk of the sun.

It was observed, that the motion of the moon appeared more quick in the
formation and dissolution of the annulus, than during its continuance. This
is particularly described by Mr. FuUarton, of FuUarton, in a very exact account
of the eclipse, as it appeared at his seat at Crosby, near Air, on the west coast
of Scotland. He writes, that " the annulus appeared to be nearly of an uni-
form breadth during the greater part of the time of its continuance, but
seemed to go off very suddenly ; so that when the disk of the moon ap-
proached to the concave line of the sun's disk, they seemed to run together



VOL. XL.] VHILOSOPHICAL TRANSACTIONS. .Ifl

like two contiguous drops of water on a table, when they touch one another;"
and he adds, that it came on in the same way. This appearance seems to be
accountable from the same optical deception as the former.

During the appearance of the annulus, the direct light of the sun was
still very considerable ; but the places that were shaded from his light ap-
peared gloomy. There was a dusk in the atmosphere, especially towards
the north and east. In those chambers that had not their lights westwards,
the obscurity was considerable. Venus appeared plainly, and continued visi-
ble long after the annulus was dissolved, and other stars were seen by some:
one gentleman is positive, that, being shaded from the sun, he discerned some
stars northwards, which he thinks by their position were in ursa major.

It was very cold at this time ; a little thin snow fell ; and some small pools
of water in the college area, where there was no ice at 2 o'clock, were
frozen at 4. A reflecting telescope of a large size, and of a much greater
aperture than ordinary, that took in the whole sun, and burned cloth very
suddenly through the tinged glass at the beginning of the eclipse, and on that
account could not then be used with safety, was that by which Mr. Short
observed the annular appearance. Some curious gentlemen found, that a
common burning-glass, which kindled tinder at 3^ SQ™, and burned cloth at
4** 8™, had no effect during the annular appearance, and for some time before
and after it.

The first internal contact of the disks, at the formation of the annulus,
was considerably below the west point of the sun's disk ; and the second
contact, at the dissolution of the annulus, seemed to be about 10° eastwards
from the north point or zenith of the disk. The breadth of the annulus
towards the south-east part of the sun's disk, was at least double of its breadth
towards the opposite part, about the middle of this appearance. Mr. M. pro-
posed to have made some estimation of the ratio of the continuance of the
annular appearance, where it was central, to its continuance at Edinburgh,
from that of the arithmetical mean between the numbers that should express
the proportion of the greatest and least breath of the annulus, to the geome-
trical mean between the same numbers ; or from the ratio of the radius to the
sine of half the arch intercepted between the two points of internal contact;
but he did not obtain these ratios with sufficient exactness.

At 3*' 31"" 43' the annulus was dissolved, after having continued 5™ 48';
the middle of the eclipse was therefore at 3'' 28™ 4g\ In this the time by ob-
servation did not agree so well with the time by computation, as in the begin-
ning of the eclipse, the difference being here about 4 minutes. The irregu-

z 2



172 PHILOSOPHICAL TRANSACTIONS. [aNNO 1738.

larities of the moon's surface occasioned the same appearances, in some mea-
sure, as at the formation of the annulus.

The beginning of the eclipse at 2^ 5™ 36*

The beginning of the annular appearance . . , , 3 25 55



Online LibraryRoyal Society (Great Britain)The Philosophical transactions of the Royal society of London, from their commencement in 1665, in the year 1800 (Volume 8) → online text (page 21 of 85)