March ii, 1892.] 



SCIENCE. 



u7 



that of the Hamitic Berbers who have lived in the vales of 

 the Atlas from the remotest times. In attributing the meg- 

 alithic monuments of western Europe and northern Africa 

 exclusively to Celtic and Germanic peoples, he proceeds be- 

 yond what archaeologists have conceded. The difficult 

 problem of the conflicting physical types among the Celtic 

 nations — the one short in stature, brachycephalic, and 

 brown, the other tall, dolichocephalic, and blond — he sum- 

 marily solves by supposing either an intermixture with other 

 types or a change in mode of life and climatic environment. 

 The Celtic language he places, as do now all leading lin- 

 guists, within the Aryan group and in that category most 

 closely allied to the Italic stock. 



The same topic is discussed very ably by the French an- 

 thropologist, Dr. E. Collignon, in one of the recent bulletins 

 of the Societe d' Anthropologic. After setting forth in strong 

 lights the embarrassing nature of the evidence, he Qnally 

 leans to Broca's opinion, that the small, brown, brachyceph- 

 alic Celts are a miied type; while the true and primitive 

 type, which we may call the Kymric, was one of tall stat- 

 ure, with reddish or blond hair and dolichocephalic crania. 

 An interesting portion of Dr. Collignon 's memoir is where 

 he points out the persistency of various physical types in 

 portions of France for many centuries, even for thousands 

 of years, as an examination of ancient sepulchres has 

 proved. 



MOTION AND HEAT. 



[Continued from p. 135.] 



But nature has other means of compensation for the molar 

 motion converted into heat. Incalculable units of heaten- 

 ergy are stored up in vegetable and animal organisms; and 

 in evaporation still more countless units of heat-energy are 

 converted first into molecular, and then into molar motion, 

 in its most terrific forms. 



Evaporation and the function it performs in the economy 

 of nature are as yet little understood. It appears to be a 

 form of expansion, and, like expansion, it increases with 

 elevation of temperature; but it does not stop when expan- 

 sion ceases, for it is well known that ice continues to evapo- 

 rate below zero C. 



It is undoubtedly the great instrumentality for converting 

 heat into motion. It is constantly acting, and in the trade 

 wind region eleven feet of the ocean's depth is annually 

 lifted up and carried oS by this silent process. Molecule by 

 molecule the aqueous vapor is torn from the liquid mass, 

 each one carrying or embodying so much heat and thus re- 

 ducing temperature; in other words, each molecule moved 

 in evaporation furnishes work in the form of motion for so 

 much of the force or energy which was dynamic in the form 

 of heat. 



Molecular motion, evidenced by gaseous expansion in a 

 closed vessel, is governed by the general laws of motion;' 

 and it seems incredible and anomalous to hold that the inert 

 molecule moved in evaporation, which unites with its fel- 

 lows as aqueous vapor, and comes down again as rain, is not 

 governed by the same laws of the motion which this force 

 or energy, in the form of heat, imparts to it in the atmos- 

 phere. 



If these laws of motion do apply to the motion imparted 

 by converted heat to evaporated molecules, we have an ori- 

 gin for the trade winds far more simple than the generally 

 supposed convection. The trade winds blow over the tropi- 



1 " Molecular Motion 1q the Radiometer," etc., p. 16. 



cal water where convection is smallest, and not over tropisal 

 land, where it is greatest. 



But it is sufficient for the present purpose to show that 

 heat is converted into motion in the process of evaporation; 

 and that even if the force or energy which, iu the form of 

 molar motion, is directly converted into heat by resistance, 

 cannot be directly reconverted from heat into molar motion, 

 there is in terrestrial nature a law of compensation which 

 tends to convert any surplus of dynamic heat into dynamic 

 motion, and thus preserve the equilibrium which has been 

 observed. 



Professor Tyndall has taught us how to trace radiant en- 

 ergy from one body to another, and how the dark or heat 

 rays may be concentrated into the more intense light rays, 

 after they have left the body which sent them forth. And 

 Faraday, Joule, Mayer, Grove, and others have taught us 

 the lavv of conservation, by which we know that this energy, 

 when it disappears, is not annihilated, and when it reappears 

 it is not a new creation. We see its manifestation in mo- 

 tion, molar and molecular; we feel it in heat, we see it in 

 light and color, and hear it in sound. The motion may 

 cease; light may be extinguished in darkness; colors may 

 fade, and sound give place to profound silence; but the en- 

 ergy or force which caused all these phenomena was the 

 same before they appeared as during their continuance, and 

 its potential existence remains after their disappearance with 

 the same measurable units as when it was dynamic, and 

 subject to observation. 



When the demon was cast out of the man and went into 

 the swine, and they ran into the sea, it was the swine, and 

 not the demon, who were drowned. He doubtless passed 

 out into demon land, ready to again become dynamic when 

 occasion offers. 



Th'S force, or energy, we are trying to trace, while dy- 

 namic, can only do so much work at one time. If it is en- 

 tirely occupied in moving a mass, it cannot do other me- 

 chanical work; and if entirely occupied in molecular motion 

 it cannot elevate temperature, nor become radiant as heat 

 or light. And when rendered entirely potential, as when a 

 ball thrown up is lodged on the roof of a house, or when 

 heat becomes latent in liquefaction or evaporation, or when 

 the sun's energy is locked up in the molecular structure of 

 vegetable and animal organisms, it can do no work at all 

 until again rendered dynamic. Its power and capacity when 

 released is identically the same, neither more nor less, than 

 when it was locked up. This is true whether it was locked 

 up as motion or locked up as heat. 



It has always ssemed to me to be unfortunate and mis- 

 leading that Professor Tyndall should have adopted "Heat 

 a Mode of Motion " as the title of the book iu which he gives 

 to the world an account of his great and valuable researches 

 in the delimitation of this force. Like the term "Mechani- 

 cal Equivalent of Heat," it results from mistaking the thing 

 done for the thing doing it, the effect for the cause. Heat 

 is not a mode of motion, and it would be just as inaccurate 

 to call gravity a mode of weight, or magnetism a mode of 

 pull, and even less inaccurate to call motion a mode of heat. 

 Motion and heat are forms or manifestations of the same 

 force or energy, and when radiant, as heat and light, it is 

 more nearly disconnected from ponderable matter than when 

 it assumes the form of molar or molecular motion. 



Motion, in all its forms, is the transference of material 

 substance, ponderable or imponderable matter, from one 

 place or part of space to another; it is the state of pondera- 

 ble matter in which the forces acting on it are not in equi- 



