236 



SCIEWCU. 



[Vol. VIII., No. U 



thus 1.628 (HgO) ; and the weight of its volume at 

 the temperature of formation, as compared with an 

 equal volume of hydrogen gas or of steam, in other 

 words, its equivalent weight, is 1,628x18 = 30,304, 

 which thus corresponds to a specific gravity of 

 1.0000 : ice, at its temperature of formation, with a 

 speciHc gravity of 0.9167, being 1,487 (HgO) with an 

 equivalent weight of 26,766. The hydrocarbon, 

 C4B10 = 58, condenses to a liquid having, according 

 to Pelouze and Cahours, a specific gravity of 0.600, 

 which corresponds to au equivalent weight, as com- 

 pared with that of water, of 17,582, or approxi- 

 mately 303 (C4H1 0), with a calculated specific gravity 

 of 0.5997. The reciprocal of the coefficient of con- 

 densation (or so-called molecular volume) of steam 

 is 18. while that of the gaseous hydrocarbon is 

 600 : 1000:: 58 : cc = 96 66. 



The chemical unit for bodies, which, like these, 

 volatilize integrally, is fixed by the density of their 

 vapors ; while for fixed species, like anhydrous 

 oxides and silicates, or for those which by heat 

 undergo heterogeneous dissociation, as for example 

 calcite and hydrous silicates, the unit tnay be the 

 simplest formula deduced from analysis, or, for 

 greater convenience in calculation in the case of 

 oxides and silicates, may have a value corresponding 

 to H = 1, or O = 8. The unit for silica thus becomes 

 SiOo^4=15; that for alumina, AI2O3 --6 = 17; and 

 that for the raagnesian silicate, SiMgg04-^-8 = 17,5. 

 Such unit-weierhts as these have been employed by 

 the writer in his late essay on ' A natural system in 

 mineralogy.' in the tables of which they are repre- 

 sented by P ; while the values got by dividing these 

 numbers by the specific gravity of the species have 

 been designated unit- volumes, and represented by V. 

 The writer of that essay, in deference to the general 

 usage of chemists, therein adopted the received 

 terminology of ' molecular weights' and 'molecular 

 volumes,' and. failing at the time to grasp the full 

 significance of his own earlier teachings as to the 

 universality of the law of volumes, spoke of the so- 

 called molecular weight as an unknown quantity, 

 although in accordance with that principle this 

 molecular weight, or. properly speaking, this equiv- 

 alent weight, is simply deduced for any body the 

 specific gi-avity of which is known. 



T. Sterry Hunt. 

 Centre Harbar, N.H., Sept 3. 



The old gorge at Niagara. 



The existence of a drift filled channel running from 

 the west side of the whirlpool on the Niagara Eiver 

 to the wide, open valley of St. David's on the north 

 face of the Silurian escarpment, has been known to 

 geologists ever since the publication of Sir C. Lyell's 

 'Principles of geology.' It was considered by him 

 as an ancient channel of the river, and it has been so 

 regarded by many geologists ever since. Arguments 

 numerous and of no slight weight can be quoted in 

 favor of this opinion. But of late years it has been 

 somewhat modified, and a disposition has been mani- 

 fested to regard this drift-filled valley of St. David's 

 as consisting of two smaller valleys, one of which 

 was excavated by a stream flowing into the place of 

 the present whirlpool, and the other into the valley 

 of St. David's. On the latter theory there may be a 

 solid barrier of rock not far underground between 

 the two valleys. In the latter no such bar can exist. 



Into the discussion of this subject I will not now 

 enter. It would require more time and space than 



can be afforded. I desire merely to mention a single 

 fact. In the course of the arguments on this point it 

 has been apparently taken for granted, if not asserted, 

 that no rock can be seen in place along this gorge, 

 but that it is filled deeply with drift almost from end 

 to end. During the recent meeting of the American 

 association I took an opportunity of going up the 

 valley from the whirlpool, and was much surprised 

 to find a ledge of limestone exposed at its bottom 

 about a hundred feet above the river. On both sides 

 it disappeared beneath the talus, but probability indi- 

 cates its continuance from side to side, especially as 

 a considerable surface is exposed. This point can 

 only be decided by quarrying. 



The importance of a bed of limestone so situated, 

 on the discussion of this question, is obvious. It does 

 not seriously affect the latter of the two hypotheses 

 mentioned above, which is, however, beset by other 

 grave difficulties. But in regard to the former it 

 proves, that, if the Niagara River ever passed that 

 way, its bed was far above the present level. No 

 concealed side-channel can be admitted in this case. 

 The space is too small. A line of drill-holes carried 

 along the course of the valley can alone supply the 

 evidence needed for a decision between the two rival 

 theories. 



It is scarcely necessary to point out the bearing of 

 this fact on those calculations of the age of the great 

 gorge which assumes that any part of it above the 

 lower rapids was merely cleaned out and not exca- 

 vated fi'om solid rock since the end of the ice age. 



E. W. CLA.YPOLE. 



Science for a livelihood. 



Some time ago I read in your journal a stirring 

 editorial, calling for young men to devote their 

 energies and life to the cause of science, and deplor- 

 ing the lack of persons who were willing to encoun- 

 ter hard work and poor pay because of love for inves- 

 tigation and study. 



Early this summer, after graduating from a first- 

 class scientific school, I made application to four 

 agricultural stations in this and other states for some 

 position, pay no consideration whatever. Having 

 been brought up on a farm, and having a first-rate 

 scientific education, a love of the natural sciences (in 

 which I have done a little practical work), and an 

 excellent physique, I thought myself fitted for inves- 

 tigation in scientific fields, particularly as I love it 

 above all else. 



In every case I received answer, ' Places all full.' 

 I have begun to doubt if investigators and workers 

 are needed in the natural or experimental sciences, 

 and think that a poor young man who cannot afford 

 to give money to the work has no call in this field. 

 Am I right ? C. B. 



Brooklyn, N.Y., Sept. 4. 



Revivification. 



In answer to your Paris correspondent, I would 

 say that quite recently, a native of India, after his 

 conversion to Christianity, gave an exhibition and 

 full explanation of the trance, as I am informed by a 

 missionary just returned from that country. Full 

 particulars can be obtained by addressing Rev. S. 

 Knowles, Gonda, Province of Oude, India. 



E. T. Nelson. 

 Ohio Wesleyan university, Sept. 6. 



