Atoms 

 Attenuation 



SCIENTIFIC SIDE-LIGHTS 



56 



of hydrogen, copper a little over 63, silver 

 108, gold 197. Heat acts upon matter ac- 

 cording to the number of atoms in a given 

 space, and not as its weight. Knowing the 

 relative weights of the atoms of the differ- 

 ent metals named, it would be possible to 

 determine by weight the dimensions of dif- 

 ferent pieces of metal so that they will con- 

 tain an equal number of atoms. If we take 

 pieces of iron, copper, silver, and gold, each 

 of such weight as that all the pieces will 

 contain the same number of atoms, and sub- 

 ject them to heat till all are raised to the 

 same temperature, it will be found that 

 they have all absorbed practically the same 

 quantity of heat without regard to the dif- 

 ferent weights of matter. It will be observed 

 that the piece of silver, for instance, will 

 have to weigh nearly twice as much as the 

 iron in order to contain the same number of 

 atoms, but it will absorb the same amount 

 of heat as the piece of iron containing the 

 same number of atoms if both are raised 

 to the same temperature. In view of the 

 above fact it seems that heat acts especially 

 upon the atoms of matter and is a peculiar 

 form of atomic motion. Heat is one kind 

 of motion of the atoms, while electricity 

 may be another form of motion of the same. 

 The two motions may be carried on to- 

 gether. ELISHA GRAY Nature's Miracles, 

 vol. iii, ch. 26, p. 42. (F. H. & H., 1900.) 



280. ATOMS THE ULTIMATE ELE- 

 MENTS OF CHEMISTRY Atomic Evolu- 

 tion. If the union of atoms is attended 

 with an ever-increasing evolution of heat as 

 they press together into closer and closer 

 associations, we should naturally expect 

 that the effect of increasing temperature 

 would be to part the atoms; and as we 

 study the phenomena of disassociation we 

 are led to the latest conception of chemical 

 philosophy, that of a condition of disasso- 

 ciated atoms out of which the material uni- 

 verse has been developed. Such isolated 

 atoms are for the present at least the ulti- 

 mate elements of chemistry, and before 

 reaching this condition all qualities which 

 distinguish substances disappear except 

 only a definite mass whose rhythmic pulsa- 

 tions the spectroscope may reveal. As out 

 of such a primal chaotic condition molec- 

 ular structures were evolved, the qualities 

 of substances appeared, and the energy of 

 nature was awakened. To discover the laws 

 of this evolution so as to follow its various 

 steps, and be able to predict the results 

 tinder given conditions, is the future work 

 of chemistry. COOKE The New Chemistry, 

 int., p. 17. (A., 1899.) 



281. ATROPHY OF EYES DUE TO 

 DISUSE Cave-fishes. But there is much 

 in the history of the development of ani- 

 mals that seems to lead to the belief that 

 eventually modifications may be due in part 

 to acts of representatives of the phylum to 

 which they belong. It is difficult to believe 



that some structural features are simply 

 the result of natural selection operating on 

 chance variations. An application of the 

 doctrine of chances to some such cases ap- 

 pears to be adverse to the conception that 

 they represent the influence of natural se- 

 lection unaided. 



A feature characteristic of most cave ani- 

 mals of widely diverse groups and classes 

 is the atrophy of the eyes, and it seems to 

 be most logical to attribute this to disuse 

 of those organs in remote progenitors, and 

 to assume that the atrophy may have re- 

 sulted from a failure of nourishment by the 

 nutrient fluid of the organs on account of 

 the loss of functional activity, rather than 

 to selection by nature of forms with succes- 

 sively diminishing eyes. The presence of 

 eyes in most cases certainly would scarcely 

 be an element of disadvantage to animals, 

 and it may be allowable to invoke some 

 other agency than chance selection. We 

 may be justified in postulating that the 

 continuous disuse of the organs would in 

 time react on the nutrition of the parts af- 

 fected, and finally atrophy or disappearance 

 would result. Like explanation would be 

 applicable to the innumerable cases of 

 atrophy of parts known to the naturalist. 

 GILL Proc. Am. Assoc. for the Advancement 

 of Science, vol. xlvi. ( 1897.) 



282. ATROPHY OF MENTAL POWERS 

 THROUGH DISUSE Darwin's Distaste for 

 Poetry. There is a passage in Darwin's 

 short autobiography which has been often 

 quoted, and which, for the sake of its bear- 

 ing on our subject of habit, I must now 

 quote again. Darwin says : " Up to the 

 age of thirty or beyond it, poetry of many 

 kinds gave me great pleasure; and even as 

 a schoolboy I took intense delight in 

 Shakespeare, especially in the historical 

 plays. I have also said that pictures 

 formerly gave me considerable and music 

 very great delight. But now for many 

 years I cannot endure to read a line of 

 poetry. I have tried lately to read Shake- 

 speare, and found it so intolerably dull 

 that it nauseated me. I have also almost 

 lost my taste for pictures or music. . . . 

 My mind seems to have become a kind of 

 machine for grinding general laws out of 

 large collections of facts; but why this 

 should have caused the atrophy of that part 

 of the brain alone, on which the higher 

 tastes depend, I cannot conceive. . . . 

 If I had to live my life again, I would have 

 made a rule to read some poetry and listen 

 to some music at least once every week; 

 for perhaps the parts of my brain now 

 atrophied would thus have been kept alive 

 through use. The loss of these tastes is a 

 loss of happiness, and may possibly be in- 

 jurious to the intellect, and more probably 

 to the moral character, by enfeebling the 

 emotional part of our nature." JAMES 

 Talks to Teachers, ch. 8, p. 71. (H. H. & 

 Co., 1900.) 



