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 minutiae, 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 HlRAM 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 Fan. 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' Fah., I have 

 immersed them in water, also immersing others, or the 

 same, if uninjured, at 800" 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 600 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 



