July 5, 1901.] 



SCIENCE 



the same conclusion with regard to Venus. 

 The results obtained at Flagstaff, Arizona, 

 by Messrs. Lowell and Douglas are in per- 

 fect agreement with these conclusions. 

 Although probably correct, the question is 

 still regarded by many as an open one. 

 The spectroscope will give the final verdict. 

 Attempts in this direction have already 

 been made by two experienced spectrosco- 

 pists, Keeler, at the Lick Observatory, and 

 Belopalski, at Pulkowa. Keeler's career 

 was closed by death, leaving this and many 

 other important researches nnfinished. 

 Such references to Belopalski's results as 

 have come to our notice seem to throw but 

 little additional light on the question. It 

 may be that the instrument has not yet 

 reached that degree of mechanical perfec- 

 tion which an investigation of such deli- 

 cacy demands ; but we may confidently 

 predict its ultimate success. 



With regard to the rotation periods of 

 Uranus and Neptune, we know next to 

 nothing. Such scanty bits of information 

 as have been obtained, however, point to 

 short periods in both cases, 8 to 12 hours; 

 here again we may look to the spectroscope 

 to give us a final answer. 



As to the physical condition of the 

 planets themselves, their adaptability to 

 the support of animal and vegetable life, 

 we certainly know a little more now than 

 was known during the early part of the 

 century. The author of the ' Positive Phi- 

 losophy ' expresses what seems to have been 

 the prevailing sentiment regarding the or- 

 thodox science of that day as follows : 

 "With rega,rd to the heavenly bodies, we 

 may obtain practical knowledge of their 

 geometrical and mechanical phenomena, 

 but all physical, chemical, physiological 

 and social researches for which our powers 

 fit us on our own earth are out of the ques- 

 tion in regard to the planets. The only 

 case in which this rule may be too severe 

 is in that of the temperature." 



There was, however, no dearth of phi- 

 losophers whose speculations disregarded 

 these modest limitations. To such the 

 planets, like our own earth, were the abode 

 of vegetable and animal life with, of course, 

 intelligent beings, perhaps greatly superior 

 to ourselves at the head. As no other use 

 in the economy of the universe could be 

 suggested for these neighboring worlds, 

 and as God could not be supposed to create 

 anything in vain, the conclusion was ob- 

 vious. More exact knowledge has, how- 

 ever, dissipated most of these plausible 

 theories. It seems at present unlikely that 

 a single one of the other planets, with the 

 possible exception of Venus can now be in 

 a condition to support the higher forms of 

 life. 



It is not now proposed to enter into a 

 discussion as to the indications of the exist- 

 ence of intelligent beings on the planet 

 Mars. Though there are some who assert 

 with great confidence that such is without 

 doubt the case, there are others whose opin- 

 ion is of equal value who are certain that 

 the last Eskimo was frozen to death on the 

 planet's equator many thousands of years 

 ago. As to the large planets, Jupiter, Sat- 

 urn, Uranus and Neptune, on account of 

 their great size and consequently slower 

 development, it is certain that they have 

 not yet reached a condition adapted to the 

 support of life, unless it be in its lowest 

 forms. There is every indication that a 

 very high temperature exists in the case of 

 all four of these planets, that they are 

 largely gaseous, consisting to a great extent 

 of vapors floating in atmospheres whose 

 depth must be reckoned in thousands of 

 miles, and that certainly no part of the 

 solid nucleus is ever seen by us. 



We have every reason for believing that 

 the sun with the attendant planets, our earth 

 included, had a common origin, that they 

 are composed of the same materials, that 

 the same chemical and physical laws pre- 



