Abraham Clark Freeman John Proffatt.

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berg ; in which he found

Cb,0, 20-36

Ta,0, 4-00

TiO, 26-59

Y,0, 23-32

Er,0, 7-63

Ce,0, 2-61

FeO 2-72

UO, 7-70

H,0 ... 402

98-84

By calculating the above, without knowing the molecular
weight of the Y,0, group but taking it to be 89*5, we arrive
at the following approximate formula :



or



approximate formula :

Cb.O^ 4TiO„ 6R0, 2iH,0,
2Cb,0„ 8TiO„ lORO, 5H,0,



which may also represent our mineral when the metallic acids
have been accurately separated and their individud molecular
weights definitely ascertained ; this we propose to do as oppor-
tunity offers. In conclusion we call attention to the fact that
this is the first occurrence of a columbo-titanate accredited to
an American locality.



Abt. XXXIX. — Origin of some Topographic Features of
Central Texas ;* by Ralph S. Tabr.

The Central Paleozoic area of Texas is a region of older
rocks exposed by the removal of the overlying unconformable
Cretaceous. The southern portion of this area has since the
very earliest times been the seat of extensive denudation as
long as any land area remained above the sea. The Potsdam
sandstone perhaps derived its sediment from the still older
metamorphic rocks. A conglomerate layer in the Lower Car-
boniferous series contains pebbles from the Silurian rocks.
The same is true of the conglomerate in the Upper Carbon-
iferous ; and the Trinity beds, the lowest of the Cretaceous
system, when conglomeritic, contain, in this region, chiefljr
Silurian pebbles. The Quaternary drift has the same peculi-
arity.

* Published by permission of Mr. E. T. Durable, State Geologist for Texas. •



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R. 8. Tarr — Topogra^phic Features of Texas. 307

Briefly outlined, geological history, commencing as far back
as I have studied it, begins with an old pre-Sub- carboniferous
land of Silurian and older rocks. At present this system ap-
pears as a patch of very much metamorphosed rock surrounded
on three sides by Cretaceous. Little is known of this region.
It is plainly a verv much degraded mountainous land-area
which has furnished thousands of feet of strata for the later
formations. As to its former boundaries little can be said ; but
I have given elsewhere* what I believe to be evidence of a
former northward extension. The tract contains marble, ^nd-
stones and schists of Lower Silurian and earlier age; but
the Upper Silurian and Devonian if they exist at all are mere
remnants. The stratigraphy is greatly complicated by faults
and folds.

In Lower Carboniferous time a submergence and long con-
tinned period of sedimentation permitted the deposition of an
extensive series of Lower Carboniferous limestone, several
thousand feet of which are still exposed between the Silurian
on the south and the overlapping Upper Carboniferous to the
north. The old shore line oi the Lower Carboniferous sea may
be plainly traced in favorable places, and here, particularly in
the upper beds, may be seeti the varied shore deposits of that
time.

A gap of unknown value, accompanied by a tilting and
slight crumpling of the Lower Carboniferous limestone series
intervened between the close of that period and the beginning
of the Upper Carboniferous. The latter beds rest unconfor-
mably upon the lower limestone. This series fully 8,000 feet
thick consists of the usual alternation of beds so typical of that
period.f The upper beds indicate an approach to tne Permian
condition of an inland sea. What intervened between the
Permian and Lower Cretaceous has not yet been made out.
That a portion of the Carboniferous had a dry land condition
for at least a part of the time is proved by the irregularity of
the contour beneath the Cretaceous. It is impossible to sav
to what extent this land condition was shared by the surround-
ing areas ; but the Carboniferous of the Colorado river valley
and the neighboring Silurian shows signs of erosion by the posi-
tion of the lowest bed of the Cretaceous, the Trinity sands of
Hill. The Trinity sands rest on the Carboniferous on the east
as low as 1250 feet above the present sea level ; but in the
western portion they are on the 2000 foot contour line. There
is a rise of 750 feet in less than fifty miles. A carefully made
map of these beds may reveal to us an interesting history of
the immediate pre-Cretaceous land. The Silurian area^was

♦ The American G^logist, forthcommj]^ number.
* f See 1 8t Annual Report Texas Oeol. Survey.



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808 a. S, Tarr — Topographic Features of Teocas.

then more elevated than the Carboniferous and the rise in the
land was from east to west.

The extensive sedimentation of the Cretaceous time com-
pletely obliterated all pre-existing topography. The deep sea
conditions and accompanying thick deposits, so plainly proved
by Prof. R. T. Hill, covered all land with a thick mantle.
When this deposit was finally raised above the sea and a new
era of erosion began, the large streams which first established
themselves commenced to flow without regard to the topo-
graphic and geologic features buried beneatn the Cretaceous.
The Tertiary beds which occupy a large portion of east Texas
mark the extension of the oceanic waters many miles farther
than at present. It is probable that the Tertiary ocean ex-
tended much farther inland than at present indicated and that
the beds have been in part removed by later erosion. It is
plain from this that the waters of the new drainage systems
emptied into an ocean not far removed from the buried Paleo-
zoic area. What were the conditions west of the Paleozoic
has not been ascertained. One stream, the ancestor of the
present Colorado, established itself in the Southern Carbonif-
erous area, and another, the Brazos, crosses this system farther
north. These streams with their tributaries have eroded the
Cretaceous from much of the Carboniferous, and the Colorado
has in addition removed the Cretaceous from a great area of
Silurian.

The history of these operations is not thoroughly plain in
every point. The extensive denudation in this Paleozoic area
must mean that this was early a region of strong erosion, and
that this condition has been continued. It may also mean
that this was the highest region of the new land. Be this as
it may the fact remams that m this area, by means of two large
rivers and several well established tributaries, a great thick-
ness of Cretaceous has been eroded away and some of the
Paleozoic removed. I'his process has established a series of
interesting topographic features, some of which throw Ught
upon the later history of the drainage systems.

The Colorado, which rises in the Staked Plains, while well
established in its lower and middle course is rapidly extending
its drainage area by headwater erosion in the plains. Deep
caiions and arroyas mark its new work in this region. Over the
Paleozoic it flows with rapid fall and a wondertully serpentine
course without regard to structural features. That it is a
superimposed stream is proved by the fact that it is now busy
eroding barriers of Silurian and other hard rocks which it has
unexpectedly reached after passing through the Cretaceous
strata. The larger tributaries flow equally without regard to
structural features ; but the smaller tributaries of more recent



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R, S. Tarr — Topographic Features of Texas. 309

origin have cut valleys in places of stnictaral weakness. This
is well shown in the case of the Waldrip coal beds, a series of
easily eroded strata, which, for a distance of forty miles, are
marked by the presence of small streams and valleys. Similar
instances are numerous.

In the erosion, accomplished under such complicated circum-
stances of accident and geological peculiarity a series of distinct
topographic outlines has been evolved. The Silurian, a region
of hard rocks, complicated by innumerable folds and probably
also retaining a well defined topographic outline evolved in

E re-Cretaceous times, is now a hilly country. A portion of the
ower Carboniferous is involved in this region of strong relief
but practically the border of the Silurian marks the beginning
of the highlands. Once partially rid of its Cretaceous cover,
this area would necessarily become a region of strong erosion
and this explains the almost complete removal of the Creta-
ceous from that surface.

The Carboniferoos on the other hand is a region of soft rock
and gentle dip, and this becomes rapidly degraded. The Car-
boniferous surface, as shown by the position of the Lower
Cretaceous upon it, was when the present drainage systems
reached it, considerably below the Silurian ; and using this
same datum plane, it is evident that very little of the Carbon-
iferous has been since removed. One chief reason for this is
that on reaching the Paleozoic the down-cutting of the Col-
orado has been indefinitely delayed by the hard Silurian and
other rocks which it is now engaged in removing. The San
Saba river, for instance, for a distance of fifteen mues above its
mouth, flows in a flood plain because of the impossibility of erod-
ing deeper until after the Colorado has removed the barriers
below. The small streams tributary to the San Saba are sim-
ilarly affected, and the same is true of other tributaries of the
Colorado, as for instance the Pecan Bayou. The chief erosion
that is being done in the Carboniferous of the Colorado river
is in the headwaters of the small streams, and the material thus
removed is deposited lower down in flood plains to be removed
when erosion at that point can proceed. A local base-levelling
is thus in process relative to the dammed-back Colorado. This
process is aided by the peculiarity of rainfall During the
greater part of the year the small creeks either contain no
water at all or so little that no work of erosion is done.
During some months tumultuous torrents rush down the stream
valleys covering the previously dry bed with water twenty
feet deep and thirty feet wide. These torrents subside very
quickly, but during their brief existence do an immense work
of erosion. The Colorado river has a wide channel for or-
dinary periods of flow ; but the high-water channel is two or



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810 It, S. Tai*r — Topographic Features of Texas,

three times as wide. A terrace twenty-five or thirty feet
above the river bed, sometimes on one side sometimes on both,
has been cut by the high water. The river sometimes rises
forty or even fifty feet, as is strikingly shown by the presence of
rafted logs near the top of Pecan trees. Great as are the
floods at such time they are incapable of carrying off all the
sediment and the flood plains are rapidly growing, at least in
the area affected by the dams in the older Paleozoic region.
Upright tree trunks, comparatively fresh, are sometimes ex-
posed for a distance of five feet above the roots, and bones of
the mastodon are found both in the alluvial deposits of the
Colorado and its tributaries.

That there has been a period of very rapid erosion just pre-
vious to the present condition is attested to by numerous points
of evidence. The Colorado is flowing in a somewhat degraded
calion above the Silurian; and where the rocks are hard
enough to resist rapid erosion this cafion character is well pre-
served. The butte type of erosion so typical of the boixiering
Cretaceous is also, 1 believe, an evidence of previous rapid
erosion. One example, the Santa Anna Mts. (so called), re-
mains in the center of the Carboniferous. There are two
bnttes, side by side and divided by headwater erosion, in Cole-
man county, fully fifteen miles from the nearest notch of Cre-
taceous. The capping stratum is a compact magnesian lime-
stone, the lowest of the Caprina division of Hill. The lower
beds are Trinity sands. The length along^the top is a little
more than a mile, the height 250 feet. Mve distinct large
creeks head in the region near these buttes, which are the last
remnant of a Cretaceous divide. The hard stratum on the top
which permits the retention of the butte outline is one of the
several strata which in the bordering Cretaceous gives the
topography its benched mesa and butte outline, a topography
so characteristic that a person can with safety predict Cretace-
ous as far as he can see the outline.

The degraded cafion character of the Colorado valley and
the sharp benched and butte outline of the Cretaceous seem
to indicate a period of hurried erosion of recent date ; and the
early Quaternary uplift which placed the Tertiary above the
sea may very well be correlated with this period.

From this it would seem that the middle Colorado originally
starting on the new Cretaceous land is now superimposed upon
the older Paleozoic, with which it is engaged in a struggle
brought about more quickly by its rejuvenation by elevation.
Owing to the vicissitudes then imposed, it is tending to reach a
temporary old age in the portion above the barriers and this
tendency is being increased by the peculiarities of rainfall.



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J, D. Hawkins — Formation of Silver Silicate, 311

The combination of geological structure and peculiarity of
erosion has given rise to three types of topographic outline.
1st, the rugged hilly topography of the plicated and metamor-
phosed Sifurian rocks, an outline in part descended from an
existing pre-Cretaceous topography. 2d5 a low hilly Carbon-
iferous area with many broad-topped hills, especially where the
Cretaceous has just been removed. On account of the de-
structibility, this area is being rapidly degraded and the caflon
character of the Colorado is therefore rapidly disappearing,
thus destroying the evidence of the recent rejuvenation. 3d, the
sharp angular outline of the butte and mesa type in the Cre-
taceous area which is rendered possible by the nearly horizontal
nature of the beds and the alternation of hard and soft strata,
but which has probably been aided also by the rapid erosion
which followed the early Quaternary uplift.



Art. XL. — On the Formation of Silver Silicate; by
J. Dawson Hawkins.

But very little seems to have been done with regard to the
formation of silicate of silver in the wet way. In Gmelin-
Kraut's Inorganic Chemistry, vol. Hi, n. 970, the following
statement is made : — " A solution of Ag,0 in 2(HF)SiF^, evapo-
rated to the consistency of a syrup, deposits hydroscopic crys-
tals of 2AgF . SiF^-f-4H,0. Out oi a solution of this compound,
ammonia precipitates a yellow basic salt, if added in small
quantitiea An excess of ammonia precipitates silicate of
Sliver." A like statement is made by Berzelius — Lehrb. d.
Chemie ; Dresden, 1836, vol. iv, p. 629. With the exception
of a paper by Dr. M. W. lies,* nothing seems to have been
done in this direction since then. With regard to the pro-
duction of silver silicate in the wet way, Dr. lies merelj
repeated the above experiment, without making any analysis
of the precipitate.

The method I have used is so siniple that it seems strange
that it has not been used before. The reaction made use of
was:

Na,SiO,+2AgNO,=Ag,SiO.+2NaNO..

The solution of Na,SiO, was made by fusing together Na,CO,
and SiO„ and dissolving the mass in water. The amount of SiO,

* Engineeriog and Mining Journal, April 19, 1884.

Am. Joub. Soi.— Thied Sbribs, Vol. XXXIX, No. 232.— April, 1890.
21



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312 Scientific Intelligence.

used was slightly in excess of the molecular proportion, and the
silicate formed was therefore slightly acid. This solution was
added to a neutral solution of AgNO,, and a lemon-vellow pre-
cipitate was thrown down. This was washed carefully with hot
water, and dried. Dried between filter paper, the salt retains
its orifi^inal yellow color, but when completely dried in a bath,
the color becomes darker. Two analyses gave the following
results :

Ag,0 1 77-42 77-41

SiO, 22-66 22-52



100-08 99-93

Ag,SiO, requires Ag,0 79-45, SiO, 20-55. This salt is, then,,
slightly acid, which agrees with the conditions of the precipi-
tatioU; as the meta-silicate of sodium was slightly acid. From
this it appears that all that is necessary to prepare a silicate of
silver of a certain composition, is the pure corresponding
sodium salt, and a neutral silver solution.

The silicate of silver is readily decomposed by all acids, and
is perfectly soluble in ammonia. It beai-s a considerable degree
of heat without decomposition, first changing its color to
brown red, then back to the original yellow, a red heat, how-
ever, resolves it into Ag, O, and SiO,.

The above is intended merely as a preliminary notice, as I
am still engaged in a further study of the salt and will publish
my results when they are complete.

Laboratory of the Globe Smelting and Refining Co., Denver, Colorado.



SCIENTIFIC INTELLIGENCE.

I. Chemistry and Physics.

1. On the Determination of Vapor Density below the Boiling^
Point, — Dkmuth and V. Meyer have modified the Meyer vapor
density method so as to allow the determination to be effected at
temperatures below the boiling point of the substance employed.
In Hermann's method this object is attained in consequence of
the diminished pressure, as is well known. The author conceived
that the same result might be reached by filling the bulb of the
Meyer apparatus with hydrogen, a gas lighter than air and also
of greater diffusibility. The apparatus used is essentially the
same. The material whose vapor-density is to be determined, if



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Chemistry and Physics, 313

solid, is introduced into the bulb, previously filled with hydrogen,
in the form of small cast sticks. If liquid, it is placed in small
tubes of Wood's fusible metal when the temperature to be em-
ployed is above 60° to 80*^, the fusing point of the metal, or in
tubes of glass, stoppered, when the temperature is below this;
the stopper being shaken out by tapping with the finger. The
bulb should have a capacity of about 100^*^, and a diameter of
three centimeters ; and the bottom which must not be too thin, is
somewhat flattened to facilitate the volatilization of the substance.
The neck is to have a diameter of not over 4 or 5 millimeters ; and
the quantity of the substance taken should be such as to produce
an expulsion of 9 to 11^^ of gas from the vessel. It is not desira-
ble with this method of working to cover the bottom with sand
or asbestos, since these substances retard the production ot vapor ;
but the bulb may be protected bjr a small spiral of platinum wire,
or some mercury may be placed m it. Results are given, in the
paper, of the determination of the vapor-density of xylene at 100**,
(40° below its boiling point), of nitrobenzene 23° and 30° below,
of naphthalene 35° below and of para-nitrotoluene 33° below the
boiling point. Also of ethyl ether at the ordinary tempera-
ture of the laboratory, 17*, its boiling point being 36°. These re-
sults show the method to give satisfactory results. — Ber, Berl.
(Jhem. Oes,^ xxiii, 311, Feb., 1890. ^ g. f. b.

2. On the Vapor-density of Aluminum Chloride,— In conse-
quence of the results obtained by Friedel and Crafts,* Nilson
and Pettersson have repeated and extended their experiments
on the vapor-density of aluminum chloride. In meeting the criti-
cism of the French chemists upon their method, they observe that
for every volatile substance, there exists a certain range of tem-
perature within which the vapor-density is a function not only of
the temperature but also of the pressure. Within this interval,
which thej call a region of gas-dissociation, they concede that the
method of Dumas gives the true vapor-density, that of Meyer (or
of Dulong, as they call it) giving values which are always too
low. But as soon as the temperature is reached at which the den-
sity of the vapor becomes constant, the same results are obtained
whichever of the two methods be employed. Since the law of
Avogadro is true only for bodies in the condition of true gases,
and since in the state of a perfect gas the density is independent
of the temperature and the pressure, and the two methods then
give identical results, it would seem that Friedel and Crafts were
hardly justified in giving the preference to one of these methods,
rather than to the other. Accordingly the authors undertook a
re-determination of the vapor-density of aluminum chloride, em-
ploying both methods for the purpose. For the Meyer method
they employed a protecting tube of Bayeux porcelain placed in a
Perrot furnace for the higher and a tube of Thuringian glass for
the lower temperatures. The density obtained, referred to air as

♦ This Journal, xxxvi, 465, Dec, 1888.



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314 Scientiji<} Intelligence.

unity, was, in the vapor of sulphur at 440° 7*30, 7*50 and 7*40;
in that of phosphoric sulphide at 518% 7*36 and 7*20; in that of
stannous chloride at 606*^, 6'34 ; in the furnace at 758** 4*80 ; at
835% 4-54; at 943°, 4-56 ; at 1117°, 4-27 ; at 1244% 4-25 ; at 1260%
4-28 ; about 1400°, 4-26 ; about 1600°, 4-08. It appears from these
results that between 440° and 758° the vapor of aluminum chloride
is in a condition of permanent dissociation and that it does not
attain a normal gaseous condition until the temperature reaches
800°, when the vapor-density becomes 4*60 and the molecular mass
133-15 corresponaing to the formula AlCl,. Between 800° and
1000° there can be no doubt that aluminum chloride has a constant
density agreeing with the composition AlCl,. For the Dumas
method, the aluminum chloride, formed by passing hydrogen
chloride gas over the metal, was sublimed directly into the cylin-
drical bulb, of about lOO*'*' capacity. After heating so long as
vapor was evolved the tu^e was sealed, cooled and weighed. It
was then opened under mercury and the volume of residual gas
measured. After washing and drying the tube it was again
weighed, the difference being the apparent mass of the aluminum
chloride and of the residual gas. It was then filled with dry air,
sealed and weighed a third time. The difference between the
second and third weighing gave the apparent mass of the air.
It was then filled with water and weighed for the purpose of
calculating its capacity. The vapors employed for heating were
those of nitrobenzene, 209°, engenol, 250°, diphenylamine, 301%
mercury, 357°, antimonous iodide, 401°, and sulphur, 440°. The
vapor-densities obtained varied from 9*92 at the lowest temperature
to 8-78 at the highest; being 9-62, 9-55, 9'34, and 9*02 at the inter-
mediate ones. These results, therefore, confirm those obtained by
Friedel and Crafts as to the general fact that there is a vapor-
density of 9*20 within these limits of temperature. But this value
is not constant and happens to exist at about the boiling point of
mercury ; while within a range of 60° above and below this point
it varies considerably, and between 209° and 440° it changes by
an entire unit. The authors conclude, therefore, (1) that starting
from the boiling point, aluminum chloride is continually disso-
ciated as the temperature rises, not becoming a perfect gas until
800* is reached ; at which point the vapor-density 4*55 is attained
corresponding to the formula AlCl, and the molecular mass
133*15; (2) that this vapor-density is departed from only very
slightly even at the highest temperatures attainable; and (3)
that hence aluminum is trivalent.

In the following paper Friedel regards the conclusions of
NiLSON and Pbttersson as too absolute. If there is disso-
ciation between 200* and 400° there must exist a vapor capable
of dissociating, and this can be only A1,C1,. Moreover, if
curves be constructed representing the results given by the
two methods, these curves do not unite with each other to
form a single curve. The determination of density between 200°
and 400° is regular, as is also that above 600°; while the portion



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Chemistry and Physics. 315

between 44p** and 600° appears to have a point of inflexion corre-
sponding to a maximum dissociation. He thinks the most natural
conclusion to be that like amylene bromhydrate, aluminum chlo-
ride has two vapor-densities ; one between 200® and 400° corre-
sponding to the formula A1X)1„ and a second above 800°, corre-
sponding to the formula AlCl,. — Ann. Chim, Phys.y VI, xix, 146,
171, February, 1890. G. p. b.

3. On the Combination of Potassium and Sodium with Am-
monia, — JoANNis has observed that when an equivalent mass of
alkali-metal is dissolved in twenty times the equivalent mass of



Online LibraryAbraham Clark Freeman John ProffattThe American journal of science → online text (page 35 of 59)