411 



SCIENTIFIC SIDE-LIGHTS 



Machine 

 Mammalia 



Force in Steel Molecular Movement. 

 There is another kind of magnet, called 

 a permanent magnet, that will remain a 

 magnet after the current is taken away. 

 The permanent magnet is made of steel and 

 hardened; then its poles are placed to the 

 poles of a powerful magnet, either electro or 

 permanent, when its molecular rings are 

 wrenched apart and arranged in a polarized 

 position, as heretofore described. Now take 

 it away from the magnet and it will be 

 found to retain its magnetism. The mole- 

 cules tend to fly back the same as those of 

 the soft iron, but they cannot because hard- 

 ened steel is so much finer grained than 

 soft iron, and the molecules are so close to- 

 gether that they are held in position by a 

 friction that is called its coercive force. 

 The soft iron is comparatively free from 

 this coercive force, because its molecules are 

 free to move on each other, so that when 

 they are wrenched out of their natural posi- 

 tion they fly back by their own attractions 

 as soon as the force holding them apart is 

 taken away. The molecules of hardened 

 steel are unable to fly back, altho they tend 

 to do it just as much as in the iron, and so 

 it is called a permanent magnet. Its mole- 

 cules also are under a strain like a bent 

 bow. (The form of such a magnet is usu- 

 ally that of a horseshoe or U.) ELISHA 

 GRAY Nature's Miracles, vol. iii, ch. 4, p. 28. 

 (F. H. & H.. 1900.) 



20 1O. MAGNITUDE OF MOUND- 

 BUILDER'S WORKS Impressive in Vast- 

 ness and Simplicity. The most remarkable 

 group [of North- American mounds] is that 

 near Newark, in the Scioto Valley, which 

 covers an area of four square miles ! A plan 

 of these gigantic works is given by Messrs. 

 Squier and Davis, and another, from a 

 later survey, by Mr. Wilson. They consist 

 of an octagon, with an area of fifty, a square 

 occupying twenty acres, and two large cir- 

 cles occupying respectively thirty and twenty 

 acres. From the octagon an avenue formed 

 by parallel walls extends southwards for 

 two miles and a half; there are two other 

 avenues which are rather more than a mile 

 in length, one of them connecting the octa- 

 gon with the square. . . . The whole 

 area _ is covered with "gigantic trees of a 

 primitive forest " ; and, say Messrs. Squier 

 and Davis, " in entering the ancient avenue 

 for the first time, the visitor does not fail to 

 experience a sensation of awe, such as he 

 might feel in passing the portals of an 

 Egyptian temple or gazing upon the silent 

 ruins of Petra of the Desert." AVEBUBY 

 Prehistoric Times, ch. 8, p. 246. (A., 1900.) 



2011. MAGNITUDE OF SUN Illus- 

 trated by Distance from Earth to Moon. 

 Since the diameter of the sun is 858,000 

 miles, there are 429,000 miles from its cen- 

 ter to its surface. Now, there are 238,000 

 miles from here to the moon. If, then, we 

 could place the earth at the center of the 

 sun, like a small kernel in the middle of a 

 colossal fruit, the moon would revolve in 



the interior of the solar globe, and the dis- 

 tance of the moon would hardly represent 

 more than half the way from the center to 

 the solar surface; to reach this surface 

 from the lunar orbit there would still re- 

 main 191,000 miles to pass over! FLAM- 

 MARION Popular Astronomy, bk. iii, ch. 2, p. 

 237. (A.) 



20 1 2. MAGNITUDE, REAL AND AP- 

 PARENT First Impressions Do Not Give 

 Deepest Truth. In April there shines to- 

 wards the west a star so far surpassing all 

 others in the heavens in brightness, that it 

 might well be believed to be the most impor- 

 tant of all the orbs discernible by us. It is 

 Hesperus, tne star of the evening, the planet 

 Venus; and, in reality, so far from being 

 the largest of all the orbs we see, there are 

 but two celestial bodies, besides the moon, 

 which are smaller than this beautiful 

 planet. The planet Jupiter, [tho] . . . 

 far inferior in brightness to Venus, is in 

 reality a globe surpassing her more than 

 thirteen hundred times in volume, . . . 

 while the splendid Sirius, which shines less 

 brightly far than Jupiter, probably sur- 

 passes Venus in bulk more than a thousand 

 millions of times. PROCTOR Expanse of 

 Heaven, p. 47. (L. G. & Co., 1897.) 



2013. MAMMALIA IN GEOLOGIC 



TIME Elephants in Northern Lands Masto- 

 don and Dinotherium. Mammalian life 

 probably culminated or attained to its 

 maximum in the Miocene and the Early 

 Pliocene periods. Then there were more 

 numerous, larger, and better-developed 

 quadrupeds on our continents than we now 

 find. For example, the elephants, the 

 noblest of the mammals, are at present rep- 

 resented by two species confined to India 

 and parts of Africa. In the Middle Tertiary 

 there were, in addition to the ordinary ele- 

 phants, two other genera, Mastodon and 

 Dinotherium, and there were many species 

 which were distributed over the whole north- 

 ern hemisphere. The sub-Himalayan de- 

 posits of India alone have, I believe, af- 

 forded seven species, some of them of 

 grander dimensions than either of those now 

 existing. We have no trustworthy evidence 

 as yet that man lived at this period. If he 

 had, he either would have required the pro- 

 tection of a special Eden, or would have 

 needed superhuman strength and sagacity. 

 DAWSON Facts and Fancies in Modern Sci- 

 ence, ch. 4, p. 147. (A. B. P. S.) 



2014. MAMMALIA OF THE WATERS 



The Whale and Porpoise Not Fishes. It 

 is very difficult, for example, to persuade 

 persons ignorant of the principles of anat- 

 omy, that the whale and the porpoise are not 

 fish, that they breathe with lungs as man 

 breathes, that they would be drowned if kept 

 long under water, and that, as they suckle 

 their young, they belong to the same great 

 class, Mammalia. Living in the same ele- 

 ment as fish, and feeding very much as fishes 

 feed, a similar outward form has been given 



