March 1, 1894.] 



KNOWLEDGE. 



65 



it a part of the surface ice that has heeti melted, and by a 

 series of such ebbs and flows Mr. Peal conceives the 

 terraced walls of the lunar craters to have been built up." 



I do not recollect ever having referred to springs of hot 

 water or ebbing and flowing. The "vents" and "heat 

 orifice " I take to be similar to those seen in terrestrial 

 volcanoes, where, as Prof. .Judd points out, some ninety 

 per cent, of the total output is steam, or heated aqueous 

 vapour. 



On page 22 of the " Theory " I call them " cold 

 volcanoes." 



On our earth we have numerous cases of submarine 

 vents, which at times raise the temperature of the water, 

 and even at last rise to the surface and form the " oceanic 

 islands." AU I assume is that these existed on the moon, 

 and during its long era of refrigeration they retarded, for 

 very long periods, the glaciation of the sea on large and 

 small sub-circular areas, a cluster of small heat orifices or 

 vents, as in Plato, at times producing a lagoon in the ice 

 sheet, as effectually as one large one. 



But in all cases a time must necessarily come when, 

 through the persistent fall in secular temperature, these 

 lagoons, in various stages of formation, solidified, and any 

 aqueous vapour subsequently given off at the old or any 

 new orifice, would be piled as snow over and around the 

 vent, and would form the well-known " cone," simulating 

 our volcanic cones, in all but their universal whiteness. 



In the deeply terraced craters — which, as a class, are not 

 overlapped by other rings — the material of the successive 

 terraces I assume to be taken from the lagoon surface by 

 evaporation, and deposited at once around the margin as 

 snow, thus at one operation forming the new terrace, and 

 still further lowering the level of the enclosed floor. 



Ice clifl's of seventeen thousand and twenty thousand feet 

 high are no part of my " theory." On page 8 of it I say, 

 "again it has been objected that snow mountains of 

 twenty thousand feet elevation are quite inconceivable, 

 but we may recollect that the gravitation on the moon 

 would be but one-sixth of ours, and that thus the lunar 

 snow in packing down, or piling up, would probably not 

 have one-fourth the same mass in an equal volume as ours. 

 Terrestrial ice on the moon would weigh lighter than cork 

 to us, and lunar snow peaks and ridges would rise as an 

 almost inconceivably light material, into an intensely cold 

 airless void. Though of such a light and flocculent 

 nature, they would appear to us, and practically be, as 

 permanent as solid rock masses. With us the lower 

 layers of deeply piled snow become pressed to ice, and 

 there seems to be no reason why the bases of lunar ranges 

 should not be of similar nature." 



I may add that it is now found that at low temperatures 

 ice becomes a non-viscous solid, like glass ; and that as 

 temperature falls, both snow and ice become more and 

 more diathermanous. 



The occurrence of small craterlets on the rims and 

 slopes of large craters and sides of mountains I, of course, 

 do not attribute to an output of " warm water," but to the 

 exhalation of .stram through orifices due to faulting — 

 similar to the formation of the crater chains over faults 

 or clefts. 



The extraordinary outcrop of minute crater cones nil 

 over the lunar surface, which is probably still going on, 

 when taken iji conjunction with the slow subsidence of 

 the lunar maria, as evidenced by the clefts, seems to me 

 a lieautiful demonstration that there is still a large store 

 of internal heat in our satellite, beneath the now glaciated 

 crust. 



I " account for the fact that the lunar plains and floors 

 of the deeper lunar craters are generally of a much darker 



tint than the higher ground upon the moon," not by 

 assuming that the former are virgin ice, and the latter 

 snow, but solely as the effect of gravitation, which 

 occasionally removes from clifls, rugged and elevated 

 regions, the meteoric dust stain, which needs must lie (and 

 accumulate) for ages on levels and gentle slopes, like the 

 outer incline of the rings — see Aristarchus, &c. — at sunrise. 

 Sibsagar, Assam. S. E. Peal. 



[If the lunar plains had acquired their dark tints by the 

 fall of meteoric matter which was originally deposited on 

 high ground, we should expect to find the darker colouring 

 near the base of the lunar mountain ranges, and that all 

 high ground would be fringed by an edging of darker shade. 

 But the dark tints are nearly uniformly distributed over 

 the lunar plains, and we seem to have evidence in lunar 

 photographs that matter of various degrees of darkness, as 

 well as white material, has flowed in streams from some of 

 the lunar craters. — A. C, Ranyard.I 



ANIMAL HEAT. 



By Vaughan Coenish, M.Sc, F.C.S. 



IN a former article it was shown how plants and 

 animals assimilate food from their environment, 

 seizing upon the same elements and building up 

 compound substances, which, though not identical, 

 are of the same general character and class in both 

 the vegetable and the animal world. 



In our last two articles we described the changes of 

 composition which take place in the life of plants and 

 animals as essentially chemical changes, following the 

 same laws and brought about by similar causes as the 

 reactions studied by a chemist in his laboratory. In the 

 growth of the animal or plant many causes co-operate 

 besides chemical causes. For example, the form and 

 structure of its parts are determined by laws which are 

 outside the ken of the chemist. But chemical forces, 

 besides building up the substances of which animal and 

 vegetable bodies are made, maintain the bodily heat 

 which is inseparable from animal life, and which, along 

 with the power of locomotion, forms to the ordinary 

 observer perhaps the most obvious and essential dis- 

 tinction between animals and plants. Lavoisier first 

 proved to the world the nature of the chemical changes 

 which occur in burning, and showed that in respiration the 

 same chemical process (oxidation) is going on. Every 

 chemical change is accompanied by a heat change. 

 Lavoisier not only recognized this fact, but he appreciated 

 its importance more than most of his immediate successors. 

 Accordingly he set himself to investigate (juantitntively the 

 heat changes which occur in the phenomena of burning 

 and of respiration, both being from his point of view 

 phenomena of oxidation. 



How well Lavoisier understood that without measure- 

 ment there is no science is shown by the fact that he used 

 the ciikirinii'ter, or instrument for measuring quantities of 

 heat, with the same diligence as he showed in the use of the 

 balance. Calorimetry, that branch of science which deals 

 with the measurement of quantities of heat, owes its origin 

 to the joint work of Lavoisier and Laplace, who were the 

 inventors of the ice-calorimeter. The principle of their 

 method was to measure the quantity of heat by the weight 

 of ice melted. Thus, in order to determine the quantity 

 of heat given out l>y one pound weight of iron in cooling 

 from the temperature of boiling water to that of melting 

 ice, the iron was placed in the central chamber of a box 

 furnished with a lid and having two annular chambers 



