2R2 



♦ KNOAATLEDGE ♦ 



[August 1, IBUS 



races, while others are too old, or may even be hut dead and 

 withered stumps. This would be a decided advance upon 

 that insect's former view ; but it would be insufficient if the 

 insect stop])ed just there. After a while the more thought- 

 ful among the insect inhabitants of that tree would perceive 

 that among the trees in the forest there were not only many 

 that differed from its own tree liome in being older or 

 younger, but many which actually differed from it in kind, 

 never resembling it closely in any one of the stages of their 

 tree growth. The insect inhabitants of the tree would then 

 perceive that trees thus differing from their tree home in 

 nature were not probably suitable abodes for the same forms 

 of life, or might even be obviously and demonstrably 

 unsuited for kindred insect races. Extending to the solar 

 system and its fellow systems the idea thus suggested only 

 as a ])arable, the life-history of orbs, different orders must 

 in all probability be entirely distinct, even though all pass 

 through the same general stages of orb life. 



For instance, the sun, regarded as an orb, is in that 

 glowing, vaporous stage, which, in the earth's case, signitied 

 infancy. Yet, as regards his work as a supporter of life, our 

 sun is in the ^ery fulness of his career. He may quite 

 jjossibly have no other special work to do in orb life ; and 

 after he has passed that stage when an orb is still instinct 

 with its primeval heat and glows with its primeval lustre, 

 he may remain a mass of idle matter, not himself the abode 

 of life like our earth, nor any longer nourishing life in other 

 worlds, as he did when in his prime. 



Again, it may be that the giant planets, Jupiter and 

 Saturn, are doing the best part of their life-work, if not 

 practically the whole, in the ]5i'esent stage of their career. 

 Unfit now to be inhabited worlds, they may ever lemain so ; 

 or the time when living creatures could exist upon their sur- 

 face may correspond to a time when the sun will have lost 

 its light and heat, and when, therefore, existence would be 

 impossible on the surfaces of any one among the giant 

 planets. 



We have at least as much reason for supposing that when 

 our earth was in sun like stage of her career, or later when, 

 in the fiery stage, she resembled Jupiter or Saturn, she did 

 work such as the sun now does, or performed such duties as 

 Jupiter or Saturn may discharge to their attendant -tt-orlds, 

 as we have for supposing that when the sun or Jupiter 

 becomes as cool as the earth, they will be inhabited by 

 ci-eatures suitable to the condition which will then exist 

 upon those respective orbs. 



With regard to orbs like INIars and the moon, which are 

 old or to all intents and purposes dead, we, doubtless, are 

 justified in assigning to them, as the probable period of their 

 life-bearing career, the time when tliey resembled tlie earth 

 in condition more nearly than they do now. Yet, though 

 orbsof both classes probably passed through such a life-bearing 

 stage, it is unlikely, nay, practically impossible, that either 

 can have resembled the earth closely at any time. It is not 

 merely that the duration of the life-bearing stage on our 

 moon, for example, must have been much less than that of 

 the corresponding stage on the earth, but that the various 

 conditions essential to life as we know it upon the earth 

 cannot have existed at one and the same time upon the 

 moon. When the moon's crust was like our earth's in regard 

 to heat, volcanic activity, and so forth, the air and water 

 must have been much less in relative amount, and such life 

 as may then have been present on the moon must have 

 existed under conditions very different from those now 

 existing on the earth. On the other hand, when the lunar 

 atmosphere was as dense as the earth's atmosphere now is, 

 its constitution must have been very different, for that 

 period corresponded to a much earlier stage of orb life ; at 

 that time also the moon's surface would have been greatly 



too hot to be the abode of living creatures such as we are 

 acquainted with on earth 



Eecognising, as we now do, the general principles at least 

 on which the evolution of animal and vegetable life pro- 

 ceeds, we can infer that even if the first forms of life on 

 Mars, on Mercury, or on the moon were, or those on Jupiter 

 and Saturn will be, akin to those on the earth — which is 

 antecedently unlikely — yet the orders of animal and vege- 

 table life developed on those other worlds could not but be 

 utterly unlike those v.hich, during the many million of 

 years of her past life, have been developed on the earth. 

 Perhaps on a much shorter-lasting planet like the moon the 

 highest orders of life developed were altogether inferior to 

 those developed on the earth. Perhaps on much longer- 

 lasting planets like Jupiter and Saturn much higher types 

 of life will be developed than have ever been developed on 

 our planet. However this may be, whether the best types 

 developed elsewhere have been or will be superior or inferior 

 to those developed on the earth, this at least is certain — 

 they must be very diflferent. Life, animal as well as 

 vegetable, in other worlds than ours, must be infinitely 

 varied. 



THE MORDEY ALTERNATOR. 



HE machine which is illustrated by the 

 accomjianying views is being brought out 

 by the Anglo-American Brush Electiic 

 Light t!orporation. Limited, for use in con- 

 nection with distribution on the ti-ansformer 

 system. It is one of a new type, and 

 possesses .several advantages of practical 



importance, and it is quite a new departure in dynamos. 



It is the invention of Mr. W. M. Mordey, and gives 



Fig. 1.— Armature of Alteenatoe. 



an output of .3.5,000 to 40,000 watts, the terminal poten- 

 tial diff'eience being l',000 volts. The speed is (!50 revolu- 

 tions per minute. Fig. 1 shows the armature, which is 

 stationary, and consists of a number of coils of narrow 

 copper ribbon, wound on cores of non-conducting material. 

 Some detached coils are shown. Each coil is bolted at the 

 broad end between two brackets, the ends of the conductor 



