201 



SCIENTIFIC SIDE-LIGHTS 



Effect 



979. EFFECT OF HEAT AND COLD 



RESISTLESS Lead Crawls Down Cathedral 

 Roof. A very curious effect of expansion 

 was observed, and explained, some years 

 ago, by the late Canon Moseley. The choir 

 of Bristol Cathedral was covered with sheet 

 lead, the length of the covering being 60 

 feet, and its depth 19 feet 4 inches. It had 

 been laid on in the year 1851, and two years 

 afterwards it had moved bodily down 

 through a distance of eighteen inches. The 

 descent had been continually going on from 

 the time the lead had been laid down, and 

 an attempt made to stop it by driving nails 

 into the rafters had failed; for the force 

 of descent was sufficient to draw out the 

 nails. The roof was not a steep one, and 

 the lead would have rested on it forever, 

 without sliding. What, then, was the cause 

 of the descent ? Simply this : The lead was 

 exposed to th'e varying temperatures of day 

 and night. During the day the heat im- 

 parted to it caused it to expand. Had it 

 lain upon a horizontal surface, it would 

 have expanded equally all round; but as it 

 lay upon an inclined surface, it expanded 

 more freely downwards than upwards. 

 When, on the contrary, the lead contracted 

 at night, its upper edge was drawn more 

 easily downwards than its lower edge up- 

 wards. Its motion was therefore that of a 

 common earthworm; it pushed its lower 

 edge forward during the day, and drew its 

 upper edge after it during the night, and 

 thus by degrees it crawled through a space 

 of eighteen inches in two years. Every 

 minor change of temperature during the day 

 and during the night contributed also to the 

 result; indeed Canon Moseley afterwards 

 found the main effect to be due to these 

 quicker alternations of temperature. TYN- 

 DALL Heat a Mode of Motion, lect. 4, p. 95. 

 (A., 1900.) 



980. EFFECT OF HUMAN INFANCY 

 AND CHILDHOOD Animal Affection for 

 Offspring Perishes and Is Forgotten. Till 

 the brain arrived, everything was too brief, 

 too rapid for ethical achievements ; animals 

 were in a hurry to be born, children thirsted 

 to be free. There was no helplessness to 

 pity, no pain to relieve, no quiet hours, no 

 watching ; to the mother, no moment of sus- 

 pense the most educative moment of all 

 when the spark of life in her little one 

 burned low. Parents could be [of] no use 

 to their offspring physically, and . the off- 

 spring could be [of] no use to their parents 

 psychically. The young required no in- 

 fancy; the old acquired no sympathy. Even 

 among the other mammalia or the birds the 

 mother's chance was small. There, infancy 

 extends to a few days or weeks, yet is but 

 an incident in a life preoccupied with 

 sterner tasks. A lioness will bleed for her 

 cub to-day, and in to-morrow's struggle for 

 life contend with it to the death. A sheep 

 knows its lamb only while it is a lamb. The 

 affection in these cases, fierce enough while 

 it lasts, is soon forgotten, and the traces it 



left in the brain are obliterated before they 

 have furrowed into habit. DRUMMOND As- 

 cent of Man, ch. 8, p. 287. (J. P., 1900.) 



981. EGG PRODUCING ALL MATE- 

 RIAL FOR THE CHICKEN The egg itself 

 contains all the materials of a complete ani- 

 mal. Bones, muscles, viscera, brain, nerves, 

 and feathers of the chicken all are pro- 

 duced from the egg, nothing being added, 

 and little or nothing taken away. 



I should, however, add "that in eating an 

 egg we do not get quite so much of it as the 

 chicken does. Liebig found by analysis that 

 in the white and the yolk there is a defi- 

 ciency of mineral matter for supplying the 

 bones of the chick, and that this deficiency 

 is supplied by some of the shell being dis- 

 solved by the phosphoric acid which is 

 formed inside the egg by the combination of 

 the oxygen of the air ( which passes through 

 the shell) with the phosphorus contained in 

 the soft matter of the egg. 



By comparing the shell of a hen's egg 

 after the chicken is hatched from it with 

 that of a freshly laid egg, the difference of 

 thickness may be easily seen. WILLIAMS 

 Chemistry of Cookery, ch. 3, p. 19. (A., 

 1900.) 



982. EGOISM, UNMITIGATED, OF 

 ANCIENT GEOLOGIC WORLD "Dragons 

 of the Prime " Slow Attainment of Better 

 Things. What spectacle could be more 

 dreary than that of the Jurassic period, 

 with its lords of creation, the oviparous 

 dinosaurs, crawling or bounding over the 

 land, splashing amid the mighty waters, 

 whizzing bat-like through the air, horrible 

 brutes innumerable, with bulky bodies and 

 tiny brains, clumsy, coarse in fiber, and 

 cold-blooded. 



" Dragons of the prime, 



That tare each other in their slime." 

 The remnants of that far-off dismal age 

 have been left behind in great abundance, 

 and from them we can easily reconstruct the 

 loathsome picture of a world of dominating 

 egoism. Nearly nine-tenths of our planet's 

 past life-history, measured in duration, had 

 passed away without achieving any higher 

 result than this a fact which for impatient 

 reformers may have in it some crums of 

 consolation. FISKE Through Nature to 

 God, pt. ii, ch. 11, p. 122. (H. M. & Co., 

 1900.) 



983. EGYPT, SEEDS AND PLANTS 



OF Superstition Ministers to Science. The 

 evidence derived from the Egyptian monu- 

 ments was not confined to the animal king- 

 dom; the fruits, seeds, and other portions 

 of twenty different plants, were faithfully 

 preserved in the same manner; and among 

 these the common wheat was procured by 

 Delille, from closed vessels in the sepulchers 

 of the kings, the grains of which retained not 

 only their form, but even their color ; so ef- 

 fectual has proved the process of embalming 

 with bitumen in a dry and equable climate. 



