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The American journal of science and arts online

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path of the meteor would be at the least 90-8 miles. Kin addi-
tion, an error of 5° be allowed in the direction of the meteor^s
path, the length would not be less than 70 miles. If even the
meteor's path was 10°, and the place of first appearance 15° in
error, the visible path would be 57 miles.

These last errors seem very much greater than can be allowed.
Mr. liallowell says, **I cannot believe the body could possiblr
have had a less altitude than 85° at the time it was first seen."
Ten degrees change in the direction of the meteor's path would
carry it about 8° towards the vertical as seen from New Haven
and New York city, a change which I think the observations
would hardly allow.

The Washington observers, to some extent confirm the Alex-
andria observation. One says it appeared first at an elevation of
50°. Dr. Mackiesays that the meteor had a luminous train ex-
tending vertically 15° to 20°. When first seen, its base was
about 30° from the horizon. The point where it was first seen,
bv Judge Boardman, would have, at Washington, an altitude of
17° 40'.

The tims of fl/ght is the most difiScult element to determine.
My purpose is not to compute the actual velocity. I wish rather
to prove that it was much more than 21 miles per second, when
the body entered the atmosphere.

Judge Boardman estimates the time at one second, and says
that it could not have been as great as two seconds. He estima-
ted it, by supposing a body to f)a8s with the same velocity over
a similar distance, and noting the interval. The person to whom
he was speaking was not able to get a view of the meteor. The
most prooable velocity from this observation, would be 86 miles :
the least velocity over 18 miles a second. The New York city
observers, reported by Prof. Loomis, saw about the same amount
of the meteor's path, as Judge Boardman. " The entire period of
visibility did not exceed one or two seconds." The velocity then



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J31 A. Newton on the Meteor of November, 1859. 191

would be not leas than 18 miles a second, and probably it was
much greater.

Mr. Mills estimated the time at two seconds. The arc passed
over seems to have been 15° or 20°. This would give a velocity
of about 18 miles a second, if his estimate of time is correct.

Dr. Mackie of Washington, says: "It was perhaps two sec-
onds in view, for I had time, after seeing it first, to grasp my
companion's arm, and point to it, before it disappeared." The
altitude of its first appearance being estimated, and not meas-
ured, the velpcity cannot be easily determined from this obser-
vation. But considerinff how liable an observer is to over-esti-
mate the time of flight, I think the velocity, so far as indicated
by his observation, is mucJi greater than 20 miles a second.

The time of flight at Alexandria was estimated nearly in the
same manner as at New Haven. The velocity which is indicated
by this observation depends on the amount of error we can allow
in the determinatioi! of the point of first appearance. Taken
strictly, we have a velocity of 260 miles a second. Though
1 should not be unwilling to admit such a velocity, if we had
valid proof of it, yet the present observation cannot be consid-
ered as furnishing it. Allowing a possible error as great as men-
tioned (p. 190) we have a velocity of 45, or 85, or 28i miles per
second. Only one person, that I am aware o^ gives a period of
time exceeding two seconds. Mr. Wallis of Sdem, Mass., says
it was in sight from five to eight seconds.

Besides these specific estimates of time, we have other reasons
of greater or less weight for calling it very short.

Mr. Marsh in his paper argues with great reason, that " the
extreme shortness oi the time occupied in its flight is proved,
not merely by the estimates of several observers, but by the fail-
nre of people in the vicinity of the explosion to distinguish the
source of the sudden flash of light seen by them, and by the im-
pression of even the most distant observers, that it fell very near
to them." The latter reason, especially, has much weight.

The light is always called a '^ flash of light," by some a sudden
or instantaneous flash.

A large number of observers state that they were unable to
call the attention of those standing by them to the meteor. It
seems that only those looking towards that part of the heuvenS|
saw it.

In a letter dated June ISth, Mr. Marsh says, " all I have since
heard from parties I have conversed with tends to confirm the
shortest estimates, the impression generally being that it was in-
stantaneous or nearly so."

In reasoning from these data^ two considerations should be
kept in mind.

1st. The natural tendency is to make the time of flight too
great, and hence the velocity, too smalL



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192 H. A. Newton on the Meteor of November, 1859.

2n(l From the moment the meteor entered the atmosphere, it
would lose velocity. The resistance which the air offers to so
rapid a motion, is enormous. If meteorites be admitted to come
in general from meteors, it may be added that they rarely enter
the ground more than two or three feet. They do not strike the
earth with a velocity at all comparable to that which meteors are
known to have, in the higher regions. They lose almost all their
velocity in passing through the atmosphere.

A careful examination of all these observations leads me to
believe that the actual velocity was as great as 36 miles a second.
If we consider the resistance of the air, and then make as large
an allowance for errors of observation as can reasonably- be
made, it seems almost impossible that it could have entered the
atmosphere with a velocity less than twenty-one miles. The
parts of the earth directly under the meteor, were by the earth's
motion in its orbit, and on its axis, moving in a line inclined
89° 31' to the path of the meteor, with the velocity of 19-023
miles. If the velocity of the meteor in this path was 21, its ve-
locity relative to the sun would then be a little more than 28^
miles. If the meteor had been moving in a parabolic orbit
around the sun, it would have had from tne comoined action of
the earth and sun, a velocity of 27*9 miles a second. If, there-
fore, as I think, can hardly be doubted, the meteor entered the
atmosphere with a velocity not less than 21 miles, it must have
been moving in a hyperbolic orbit.

We have been accustomed to consider the solar system as filled
with small planetoids, millions of which, each day, come into the
atmosphere, and are burnt up, causing the shooting stars. Now
we find that we must, in all probability, add one, and no doubt
innumerable other similar bodies to the stellar spaces. It opens
a new view of creation.

It must not hence be imagined, that the meteors and shooting
stars all come from the stellar spaces. The periodicity of the
August and November meteors, shows plainly that they are from
permanent members of the solar system.

This meteorite did not come from the moon. If we could sup-
pose a lunar volcano to throw out a body with such an enormous
velocity, that body must come to the earth, nearly from the di-
rection of the moon. But the moon was at that time about 120**
from the direction of the meteor's path.

The recent researches, respecting the transformation of motion
into heat, throw some light on the subject of shooting stars.
When these bodies come into the atmosphere, the motion they
lose is transformed into motion of the air, heat, light, sound, and
probably other forms of energy. If it was all transformed into
heat, it would be easv to compute the amount due to the loss of
a given velocity, if they have a motion of their own, and their
directions are subject to no law, it is easily seen that the avera^



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H, A. Newton on the Meteor of November, 1850. 193

velocity is much greater than 19 miles a secojid. A body weigh-
ing one pound, and moving 25 miles a second, has momentum
sufficient to raise (26x5280)^ -^ 2^=271,500,000 pounds one foot
By Joule's equivalent the raising of 772 pounds one foot, corres-
ponds to the neat necessary to raise one pound of water one de-
gree Fahrenheit. If the capacity of the meteoric substance for
heat is 0*2, (that of iron is 0*12,) the loss of a velocity of 26
miles would be equivalent to heating (271,500,000-r0-2)-T-772=
1,760,000 pounds of the substance one degree Fahrenheit, if the
whole of the motion was transformed into heat A very small
fraction of this heat would doubtless suffice to burn up, or dissi-
pate, any substance whatever.

It is often urged, that the shooting stars cannot be solid bod-
ies, since of the millions that daily enter the atmosphere, so few
come to the ground. The above calculation shows that the heat
generated may be ample to valorize or dissipate them.

The shooting stars need not in general be large bodies. The
apparent size is due to irradiation, and indicates, not amount of
matter, but rather amount and intensity of light Thus the stars
though often spoken of as mere points have disks. The diame-
ter of stars of the first magnitude was estimated at 2' by Tycho
Brahe. The telescope has shown that this disk is spurious. If
these stars are equal in size to the sun, Tycho's estimate makes
their diameters 50,000 times too great.

It has been estimated that the light of the sun's sur&ceis four
or five times as great as that of the same surface of the lime in
the calcium light It is also estimated that the light of the sun
is 20,000,000,000 times that of Sirius. A simple calculation
shows that an inch slobe as brilliant as the calcium light, would
give at over 100 miles distance as brilliant a light as a star of the
first magnitude. The estimates which are used as the basis of
calculation are confessedly very vague, yet they show that a very
small body may furnish as much light as a shooting star. Such
a body would naturally burn up without passing through the
atmosphere.

I can therefore see no reason, as some persons do, to make
a marked distinction between the different classes of meteors.
Those which furnish meteorites, those which explode with a
loud report, and those of all decrees of brilliancy which are not
heard to explode, all seem to belong to one class, and to differ
from each other no more than substances on the earth. That
some are solid and others aeriform is not impossible. Differ-
ences of chemical constitution, size, velocity, and orbit exist,
and these may account for the variety of appearance.

^ol«.-— Since the above was in tjjse, the meteor of Julj 20 seems to famifih better
data for proTing that meteors sometimes come from the stellar spaces.
AM. iOUB. SCL— SECOND SERIES, Vox. XXX, No. 89.— SEPT., I860.

25



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194 Prof. J. P. Cooke on the Variatum of Constitution of a



Art. XVill. — OrysiaUine form not necessarily an indication cf
definite Chemical Composition: or^ on the possible variation ^
constitution in a mineral species independent of the Phenomena of
Isomorphism. By JosiAH P. CoOK£, Jr., A. A.S., Professor of
Chemistxy and Mineralogy in Harvard College.**^

Ik a memoir presented to the American Academy of Arts and
Sciences in September, .1855,t I described two new oomponnds
of zinc and antimony which I named stibioUzincyle and stibiotri-
zincyle, on account of their analogy in composition to the metallic
radicals of organic chemistry. The symbols of these compounds
are Sb Zn* and Sb Zn* ; and they are distinguished by the high
perfection of their crystalline forms, the last being still farther
characterized bjr a most remarkable property of decomposing
water quite rapidly at 100^ C. I stated in the same memoir
that crystals of these two compounds could be obtained contain-
ing proportions of zinc and antimony differing very widely
from those required by the law of definite proportions ; and I
also traced out the relation between the composition of die
crystals, and that of the menstruum in which they are formed.
It is my object in the present paper to consider the bearing of
these facts, already fully described, on the idea of mineral spe-
cies, and to offer a few suggestions which I hope may be of
service in determining the true chemical forrou1» of many min-
erals, and thus in simplifying the science of mineralogy. But
in order to render myself intelligjlble, it will be necessary to
recapitulate very briefly the facts in question, referring to the
original memoir for the full details.

The crystals both SbZn* and SbZn' can be obtained witb
great readiness. It is only necessary to melt together the two
metals in the atomic proportions, and when the metals are fully-
alloyed, to proceed exactly as in crystallizing sulphur. The
melted mass is allowed to cool until a crust forms on the surfiice,
which then is broken, and the liquid metal remaining in the
interior poured out. On subsequently breaking the crucible, the
interior is found lined with magnificent metallic crystals, whicby
when not tarnished by oxydation have a silver^white lustre. In
the course of my investigations on these compounds, crystalliza-
tions were made, or attempted, of alloys, differing in composition
by one half to five per cent, according to circumstances, from
the alloy containing 95 per cent of zinc, to that containing 95
per cent of antimony ; out only two crystalline forms were mcT'
ved, that of Sb Zn* and that of Sb Zn^ The crystals of the

* Communicated by th« Author.

f TniDsacUoiu of th« American Academj of Arti and Sciences, New Series,
vol. V, p. 887. Thii Jour. [2], m, 28S.



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mineral species independent of Phenomena of Isomorphism. 195

two oompounda both belong to the trimetric system ; but they
diifer from each other, not only in their crystallographic elements,
but also in their whole " habitus." Stibiotrizincyle crystallizes
in long acicular prisms, which ^roup themselves together into
larger prismatic affgregates; while stibiobizincyle crystallizes in
brood plates, which twin together on an octahedral face, and
form a verj characteristic cellular structure. This very striking
difference m the character of the crystals proved to l>e an im-
portant circumstance in the investigation, as it enabled me to
distinguish with certainty between the two compounds, even
i¥hen the &ces of the crystals were so imperfect that a measure-
ment of angles was impossible.

The most remarkable result of the investigation, and the one
to which I wish to direct especial attention, is the fact that each
of the two crystalline forms was found to be constant under very
wide variations in the per-oentage composition of the crystals.
As this is a point of great importance, it will be necessary to en-
ter more into detail, considering in the first place the crystals of
Sb Zn'. The crystals of this compound are obtained in the
greatest perfection from an alloy containing the two metals in
just the proportions represented by the formula, namely, 42-8
parts of zmc> and 67*2 parts of antimony. They are then com-
paratively large, generally aggregated, and, as the three analyses
cited in the accompanying Table indicate, they have the same
composition as the alloy.

Composition of the alloy by
syntheais.

Per eeot Per cent
of Zn. of 8b.

42-80 68-20

(4 it

U M

On increasing gradually the amount of zinc in the alloy up to
48*7, the crystals continued to have the composition of the alloy ;
and the only difference which could be observed in their charac*
ter was that they were smaller, and more freauently isolated*
Between these limits the whole mass of the alloy exhibited a
strong tendency to crystallization ; and by pouring it, as it cooled,
from one vessel to another, it could be crystallized to the last
drop. On increasing the amomit of zinc in tho alloy to 50*7 per
cent, the amount of zinc found in the crystals was uniformly
less than it was in the alloy ; but no closer relation between the
two could be detected, owing, undoubtedly, to the unavoidable
irregularity in the crystallization of the alloys which contained
more than 50 per cent of zinc. This arose from a peculiar pastjr
condition which the liquid mass assumed at the point of crystalli-
zation. Definite crystals, however, were obtained from an alloy
of 60 per cent zinc containing 55 per cent ; above this the crys-



CompoeitioD of ihe crystals by




analysis.


Percent


Per cent Sum.


of Zn.


ofSb.


4315


66-93 100-08


43-06


56-60 99-56


42-83


57-24 100-07



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.106 Prof. /. P. Cooke on the Variation of Constitution of a

Uls became less and less abundant, and gradually faded oat,
although the alloy of 86 per cent of zinc exhibitea a radiated
crystalline texture ; and a trace of this structure could still be
discovered even in the alloy containiog only 4 per cent of anti-
mony. It was very interesting to trace the gradual fading out
of the crystalline structure, as the character of the phenomenon
was entirely analogous to that which may be noticed in mauy
crystalline rocks.

Finding that the crystalline form of Sb Zn' was constant un-
der so great an increase of the proportion of zinc in the crystals,
it might be supposed that, on returning to the alloy of 42*8 per
cent of zinc and increasing the amount of antimony, we should
obtain crystals containing an excess of antimony ; but so far is
this from being true, that the slightest excess of antimony en-
tirely changes the character of the crystallization. On crystalli-
zing an alloy containing 41*8 per cent of zinc, not a trace of
any prismatic crystals could be seen ; but in their place there
was found a confused mass of thin metallic scales, which, as will
soon be shown, are imperfect crystals of Sb Zn». Thus it ap-
pears that, although perfectly formed crystals of Sb Zn' can be
obtained containing 65 per cent of zinc (that is, 12 per cent
above the typical proportions), they cannot be made to take up
the slightest excess of antimony.

Let us pass now to the crystals of Sb Zn*. In order to obtain
crystals having the exact typical constitution, it was found ne-
cessary to crystallize an alloy at least as low as 31*5 per cent of
zinc. At this point large compound crystals are obtamed corres-
ponding to the large crystals of Sb Zn^ ; and the same was true
of alloys down to 27 per cent of zinc. Between these two lim-
its (namely, alloys of 81-5 and 27 per cent of zinc) the crystals
formed were found to have the theoretical composition of So Zn*,
indicating of course a tendency towards this point ; but on in-
creasing or diminishing the amount of ainc in the alloy beyond
these limits, the composition of the crystals immediately iM^an
to vary in the same airection as that o^ the alloy. The crystals
of Sb Zn' containing an excess of zinc are smaller and more
frecjuently isolated than those having the exact theoretical com-
position. A similar fact, it will be remembered, is true of the
crystals of SbZn».

At the alloy of 33 per cent of zinc, the definite crystals of
Sb Zn' begin to disappear, and are succeeded by thin metallic
scales, which are obviously imperfect crystals of the same form.
This was established, not only by the obvious law of continuity
noticed in the different specimens (the perfect crystals gradually
passing into the scales), but also by the peculiar mode of twin-
ing, which was the same with the scales as with the large crys-
tals, forming the peculiar cellular structure already referred to.
Moreover, the angle between two scales tJius united was found



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mineral species independent of Phenomena of Isomorphism. 197

to be equal to the basal angle of the perfect crystals, at least as
nearly as could be measured. These scales continue up to the
alloy of 41*8 percent of zinc, becoming, however, less abundant
and less distinct. Several specimens of them were analyzed ;
but no regularity could be detected in their composition, except
that they all contained a much larger amount of zinc than the
alloys in which they were formed.

Crystals of Sb Zn^ containing an excess of antimony were
readily obtained from alloys containing less than 27 per cent of
zinc. Tbey became more and more imperfect as the excess of
antimony increased, and finally faded out altogether in the alloys
below 20 per cent of zinc. It is evident, therefore, that definite
and perfect crystals of Sb Zn^ can be obtained with a large ex-
cess either of zinc or antimony above the theoretical composi-
tion. It is also evident that, of the two compounds, SbZu* is
the most stable, — first, because it is formed to the exclusion of
Sb Zn* in all alloys containing less zinc than the amount corre-
sponding to the typical composition of the last compound ; and
secondly, because the crystals retain the typical composition un-
der quite a wide variation (viz. between 81*5 and 27 per cent)
in the composition of the alloy.

The facts above stated are fully illustrated by the following
Table, which gives the results of a large number of analyses of
crystals of both compounds formed in alloys containing different
proportions of the two metals : —

AnalyHs of the Crystals formed in the Alloys of Zinc and Antimony,



Stibiotrizincyle. |


Stibiobuincyle. |


ComiMwitionortha


Compoeitioa of the cryetab




Compoeitioo of the crystals


aJloys by ayntbeiia.


by analyvis.


alloy* by syniheeii.


by analyiii.


Pur cent


Per cent


Per cent. Percent i


Sum.


Per cent.


Pur cent


Per cent


Perce t


Snm.


oTZn.


of Sb.


ofZn.


ofSb


ofZo.


of Sb.


ofZo.


ofSb.


70-41)


29 60


64-16


86-77


99-92


88-00


6700


86-87


64-67


99-94


66 60


88 60


6100


8900


*10000


8800


67-00


86-40


64-60


1 10000


6460


86 60


68-60


41-44


99-94


82-60


67-60


84-62


64-92


99 64


....


....


66-49


44-42


99 91


82-60


67-60


84-61


6689


tioooo


60-60


89-40


6600


46 09


100-09


81-60


68-60


88-96


66 09


100-04


58-60


41-40


6089


49-29


99-68


2960


70-60


88 62


66-88


1 10000

jioooo


66 60


48-40


49-92


6006


99-97


29-60


70-60


8862


6688


64-70


46-80


48-26


6142


99 68


27 60


72-60


8886


66-81


99 66


62-70


47;80


4nii


62-68


fioooo


26-60


78-60


8208


67-60


9968


.. .-


.*^. . '


Sw


....


....


26 00


74-00


80-74


6906


99-80


60^0


g9'80


68-11


Moo-oo


26-60


74-60


80-43


69 61


99^4


60-70


fln»30


4^-4*


6866


ffoooo


26-Od


76-00


2988


70-20


10008


48-70


K^80


48:61s


61-84


100 00


24-60


76-60


28-76


71-24


10000


46-70


^9r30


46-X
.44-26


6823


Moo'oo


28-60


76-60


27-98


71-86


99-78


44-80


6^0


66-78


MOO-OO


22-60


77-60


26-62


78-27


9989


48-80


6i20


4404


6696


f 10000


21-60


78-60


24-88


74-74


99-67


42-80


68-20


48-16


66-98


10008


2012


79-88


20-68


79*42


100-00


4280


68-20


48 06


66-60


99-66












42-80 68-20


4283


67-24


100^7













* Iq this anftljrris the Aotimonj' only "was determined,
t In this aDAlyeU the sine only was determined.



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198 Prof, /. P. Cooke on ike Variation of ConstUutian in a

The relation between the compoaition of the crjrstals Sb Zn*
and that of the allo^ in which they are formed, is discussed at
length in the memoir already referred to. It is there shown to
be a very simple function of the mass of metal which is in ex-
cess in the alloy, and of the force which determines the union of
the elements in definite proportions. The whole order of these
phenomena seem to the Author to ]3oint to«the existence of a
power in the mass of metal which is in excess in the alloy, to
disturb the action of the force, whatever it may be, which tends
to unite the elements in definite proportions. There is, in the
first place, a strong tendency in the elements to unite and form
crystals having the exact typical composition ; and secondly, this
tendency is only overcome by a certain excess of either metal in
the alloy. Then, again, the crystals of one compound obviously
interfere with those of the other. This certainly has the appear-
ance of one force interfering with the action of another, — the
force of mass (if I may so call it) perturbing the action of the
chemical force. But it is not my object at present to enter into a
discussion on the cause of this variation. Moreover, since such



Online LibraryRobert StevensThe American journal of science and arts → online text (page 83 of 120)