254 
SCIENCE. 
twelve days, the younger the germ the less time 
should it be exposed to chromic acid. After having 
been in alcohol a week it is transferred to a sherry 
wine colored solution of bichromate of potash for a 
period sufficient to harden it. 
With a cataract needle the investigator will then 
cut a trench around the embryo, cutting through 
the vitelline membrane, which fixes the embryo to 
the vitellus, and then lift it away and remove it from 
the latter, which, brittle and crumby, cannot be cut. 
The staining in a solution of carmine, as described 
for adult brains in this paper, will require from one 
to four days, according to the size of the embryo. 
Of each stage three series of sections are necessary, 
one transverse, one horizontal, and a third, the most 
important, sagittal, that is parallel to the median 
plane. 
All these minutias, however wearisome they will 
prove, are necessary, and he who has thus with his 
scalpel, reagents and razor, constructed an open 
volume of natural specimens, will find himself 
richly rewarded by the richness in detail, the mani- 
fold character of the morphologies, and the sugges- 
tive character of the relations exposed. 
The material for such a study can be obtained in 
a fresh state from no one locality. The student 
residing in New York will have to take a vacation 
trip to the Mississippi ; he living in Chicago a cor- 
responding trip to the Atlantic coast. 
In the West he will find the great lake catfish, 
the lake sturgeon, the Amia calva, the gar-pike, 
and the remarkable spatularia, the brains of all of 
which should be studied. Possibly he may obtain 
the fresh water lamprey (Hylomyzon), but one 
brain which he should not neglect is that of the 
blind fish of the Kentucky caves, whose examina- 
tion is destined to clear up somewhat the true rela- 
tions of the lobi inferiores and the optic lobes. On 
the Atlantic coast all the bony fish, obtainable in 
the fresh waters of the West, besides a rich variety 
of salt water forms, also the lamprey, the shark and 
ray are obtainable. A trip to the Bermudas or the 
Florida coast, occupying about two weeks, will in- 
crease the student’s repertoire with a host of tropi- 
cal and sub-tropical genera. 
WEIGHT, SPECIFIC GRAVITY, RATES OF AB- 
SORPTION, AND CAPABILITIES OF STAND- 
ING HEAT OF VARIOUS BUILDING STONES. 
By Hiram A. Cutting, Ph. D., State Geologist Vermont. 
Having during the past year instituted, and carried out, 
a series of experiments to ascertain, as nearly as possible, 
the capabilities of the various materials used in the con- 
struction of so called fire proof buildings, to stand heat, 
I submit, in tabulated form, the result of such experiments, 
hoping they may be of use to the architects, quarrymen 
and Insurance companies of our country, and also of 
some interest to those interested in science. 
In connection with the capabilities of the various build- 
ing stones to stand fire and water, I have taken their 
specific gravity, and weight per cubic foot, so that the 
identity of the various stones could at any time be com- 
pared, and if in the working of a quarry there was a 
change in gravity, or weight, that it could be easily de- 
tected, and thus all who choose could know whether the 
tests given would apply or not. 
I have procured sample specimens of the most import- 
ant building stones in the United States, and Canada, 
and, after dressing them into as regular form as possible, 
three by four inches, and two inches in thickness, I have 
taken their ratio of absorption, which ratio I have ex- 
pressed in units of weight, according to the amount of 
witer taken up. If 450 units of stone absorbed one unit 
of water, I have expressed it thus : 1 + 450, meaning 
that the stone weighed 450 units when immersed, and 
451 when taken from the water. 
To accelerate the process of absorption I have placed 
the specimens in water under the exausted receiver of an 
air pump. I find that in this way as much water is ab- 
sorbed in a few minutes as in days of soaking. When 
specimens were removed from the water, I have, before 
weighing, dried their outsides with blotting paper. In 
relation to the specific gravity, I have not followed “ Gil- 
more’s ” rule in full. He weighed the specimens in air, 
immersed them in water, and allowed them to remain 
until bubbling had ceased and then weighed them in 
water, after which he took them from the water, dried 
them outside with bibulous paper, and weighed them 
again in air. From this last weight he subtracted the 
weight in water, dividing the dry weight by the differ- 
ence. 
This gave a specific gravity subject to two sources of 
error. I have followed the more frequent custom of 
weighing the dry stone, using pieces of two or three 
pounds in weight, and then immersing them in water. 
After the usual saturation I have taken their weight in 
water, subtracting it from the dry weight in air, and 
then dividing the dry weight by the difference. This 
gives the specific gravity of the rock itself, as usually 
found, which is what we desire, and I believe as it would 
generally be in buildings constructed of the given ma- 
terial. The specimens were previously dried by long ex- 
posure to a temperature not exceeding 200° Fah. To 
verify this I have taken specimens from the quarries di- 
rect, and after weighing, have brushed them over with 
paraffine dissolved in naphtha, weighing them again so 
as to ascertain the exact amount of paraffine, which 
made no visible change in the stone, other than to keep 
out water. I have then weighed in the usual way, and 
thus obtained the exact specific gravity of the stone as 
in the quarry, and I find my method used, as stated, to 
give the best results, and so have adopted it. 
After this I have placed them in a charcoal furnace, 
the heat of which was shown by a standard pyrometer. 
In many instances I have placed them side by side with 
dry specimens, but have been unable to note any marked 
difference in the action of heat, beyond this, that the dry 
specimens became sooner heated, I have, however, no 
doubt that the capacity of a stone to absorb water is 
against its durability, even in warm climates, and vastly 
more so in the changeable and wintry climate of New 
England. It is here often frozen before any considerable 
part of the moisture from Autumn rains can be evapor- 
ated, 
When the specimens were heated to 600 0 Fah., I have 
immersed them in water, also immersing others, or the 
same, if uninjured, at 8oo° and 900°, that is if they are not 
spoiled at less temperatures. I find that all of these 
samples of building stones have stood heat without dam- 
age up to 500°. At 6oo° a few are injured ; but the in- 
jury in many cases commences at or near that point. 
When cooled without immersion they appear to the eye 
