SCIENCE. 



287 



Besides the seasonal variations, there was a gradual 

 lowering of the temperature which produced the phenomena 

 known as Glacial, and which characterized the Glacial pe- 

 riod, as it is generally termed. The appearance of man at 

 this stage may be conveniently studied from the point of 

 view of the river deposits of Crayford, in Kent, a place re- 

 markable for the large number of mammoths, bisons and 

 horses, which have there been exhumed. Numerous flint 

 splinters of unmistakeable human workmanship were dis- 

 covered in the Spring of the present year, under conditions 

 which indicated the exact spot on which an ancient hunter 

 sat and chipped them, and these chips being so little dis- 

 turbed that it was found possible to put together several 

 large masses, and to restore some of the original nodules 

 from which the implements were made. In one case I 

 was fortunate enough to discover an implement rudely 

 chipped all around which indicated that the primeval 

 hunter of the mammoths, bisons and horses of that neigh- 

 borhood was in the same state of culture as the man 

 who hunted reindeer in the valley of the Thames in the 

 next or the latest stage of the Pleistocene period. The river 

 valleys of the south of England are covered with sheets of 

 gravel termed river drift, and these contain vast numbers of 

 reindeer, as well as bisons and horses, and were accumu- 

 lated at a time when the climate was severe. In these, nu- 

 merous implements were discovered, extending from Peter- 

 borough, in the north, as far as the channel. Similar imple- 

 ments are also met with in France, and occur n Spain, 

 Italy, Greece, Northern Africa, and Egypt ; they also occur 

 in Asia Minor, and have been found throughout the penin- 

 sula of India. They indicate a primeval condition of sa- 

 vagery from which mankind has emerged, which was uni- 

 form over the whole of this area. It is not a little strange 

 that the river-drift hunter should have used implements of 

 precisely the same shape and material in the Indian jungles, 

 in the forest-clad shores of the Mediterranean, and in the 

 wilds of Middle and Northern Europe. No human remains 

 assignable to this age are sufficiently perfect to allow of our 

 passing opinion of man's physique, but they tell us that he 

 was a man and not a " missing link." The researches of 

 Dr. Abbott on the river gravels of Trenton appear to esta- 

 blish the fact that the river-drift man was an inhabitant of 

 America during the time when the mammoth was living in 

 the valley of the Delaware. The paleolithic implements of 

 the ate Pleistocene river beds are rude and simple, although 

 they show a considerable advance from the simple flake, 

 which is the only trace left by the man of the middle Pleis- 

 tocene. As regards the man of that period, it is probable 

 that the plateau of Central Asia was the centre from which 

 the race diverged. 



On the bottom of the caves of Cresvvell, in Yorkshire, 

 were found river-drift implements in association with vast 

 numbers of gnawed bones of both living and extinct ani- 

 mals, brought in by hyenas, while in the upper portions 

 were found implements of a higher type, composed of flint 

 and carved bone. Among these was the incised figure of a 

 horse ; these imply a higher type than that of the river- 

 drift, and belong to a state of culture known as that of the 

 cave man. It seems to be unquestionable that the cave 

 men were preceded in their habitations by the river-drift 

 men, in some places at least, and that of the two sets of im- 

 plements now found the ruder belongs to the latter race. 

 It has been a debated question whether the civilization of 

 the cave man was the outcome of the development of that 

 of the river-drift man. The evidence seems to indicate that 

 they must be classed either as two distinct races or as two 

 sections of the same race, which found their way into 

 Europe at widely different times — the river-drift men being 

 of far greater antiquity in Europe than the others. The 

 discoveries of late years tend to confirm the identification of 

 the cave men with the Esquimaux. We infer that the cave 

 men ciothed themselves with skins, for instruments for 

 dressing skins are found precisely like those now employed 

 for that purpose by the Esquimaux. That they wore gloves 

 is shown by carvings which represent them, and there is 

 reason to believe that they were in the habit of decorating 

 their persons in various ways. The art of representing 

 wild animals in carvings and by sculpture was carried to a 

 high stage of excellence by the cave-dwellers, and it is 

 doubtful if an artist of the present time could do better 



work, or even as good, with the rude instruments used by 

 them. One of the most interesting examples of their skill 

 is shown by representation of a mammoth, and we know 

 that the extinct creature is faithfully por-trayed, because 

 its remains have come down to us perfectly preserved in 

 the ice of the northern latitudes. In various ways the 

 habits of the cave men correspond to those which now 

 prevail among the Esquimaux. 



NATURAL SELECTION. 



A curious instance has occurred showing the difficulty 

 of explaining the true theory of " Natural Selection," 

 even to scientific men ; it is therefore not surprising to find 

 that those who are opposed to the principle from religious 

 motives, fail to realize what is understood by the term. 

 In a letter to Nature, Mr. Charles Darwin states he is 

 sorry to find Sir Wyville Thompson does not understand 

 this principle of natural selection as explained by himself 

 and Dr. Wallace, as, if he had clone so, he would not have 

 wrttten a sentence found in his introduction to the voyage 

 of the Challenger, as follows; "The character of the 

 abyssal fauna refuses to give the least support to the 

 theory which refers to the evolution of species to extreme 

 variation, guided only by natural selection." This, says 

 Mr, Darwin, is a standard of criticism not uncommonly 

 reached by theologians and metaphysicians, when they 

 write on scientific subjects, and asks, " can Sir Wyville 

 Thompson name any one who has said that the evolution 

 of species depends only on natural selection ?" and con- 

 tinues, " as far as concerns myself, I believe no one has 

 brought forward so many observations on the effect of the 

 use and disuse of parts, as I have done in my ' Variations 

 of Animals and Plants under Domestication,' and those 

 observations were made for that special object. I have 

 also there adduced a considerable body of facts, showing 

 the direct action of external conditions on organisms, 

 though, no doubt, since my books were published, much 

 has been learnt on this head." 



PROPAGATION OF SOUND BY LIGHT IN 1811. 



In searching a volume, dated 181 1, for papers relating 

 to the introduction of illuminating gas, we noticed a paper 

 by Modeste Parolette, entitled " inquiries Concerning the 

 Influence of Light on the Propagation of Sound," taken 

 from the Journal de Physique, Vol. LXVI1I. 



Although Parolette cannot be said to have anticipated 

 those physical facts, the knowledge of which enabled 

 Edison to design that wonderful instrument, the 

 Tasimeter, and since developed by Bell in his Photophone, 

 still Parolette seemed to be on the right track. 



In opening his subject, Parolette states that the object of 

 his inquiry was the relation which subsists between the 

 action of light and the vibrations of sonorous bodies, 

 and he actually made an instrument for measuring the 

 effect of light on sound-vibrations, and called it the Pho- 

 nometer. 



Parolette's experiments were rude compared with those 

 of more recent date, but it most be remembered that they 

 were made seventy years ago. He used no mirrors for con- 

 centrating a beam of light, but relied merely on the 

 natural properties of light without such aids. He says, 

 "As it is known that the vibrations of elastic fluids are 

 always analogous to those of the particles of the sounding 

 body, and that if two strings, belonging to two instru- 

 ments, be in unison, when one is touched the other will 

 vibrate and emit a perceptible sound ; I availed myself 

 of these properties in the construction of my apparatus, 

 and in determining the object of my inquiry. 



The Phonometer consisted of two violins placed on a 

 horizontal plank ten feet long and eight inches wide. Hav- 

 ing tuned these instruments to the Paris diapason, he fixed 

 a piece of paper to the second string of one of them to 



