Apbil 23, 1909] 



SCIENCE 



659 



but coming out with an equation of the same 

 nature as 7. As I understand it, he proceeds 

 as follows : 



Combining (1) and (2), for any velocity, 



dE = vdM, 



and replacing dM from (6) and dE from (5), 



Y-dm = vmdv + v'dm. 

 Integrating, 



m/m" = V/ yv- — v', ( 8 ) 



in which as before, when v is zero, m is m", the 

 mass of the object at rest, and when v' is Y^, 

 the mass is again equal to infinity, for the 

 same reason as given previously. Professor 

 Lewis interprets this equation thus : " Accord- 

 ing to equation (8), any body of finite mass 

 increases in mass as it increases in velocity, 

 and would possess infinite mass if it could be 

 given the velocity of light." 



Consider a body in a rarefied atmosphere 

 and set in motion by the gas particles. It 

 seems to me that Professor Lewis's reasoning 

 will apply equally here, and then a body mov- 

 ing with the velocity of the gas particles 

 should gain infinite mass. According to my 

 interpretation of the equations, when the body 

 did gain the velocity of the gas particles, an 

 infinite number of them, an infinite mass, 

 would have accumulated on the object. 



I am inclined to think myself that these 

 troubles of mine are due to unfortunate word- 

 ing. If so. Professor Lewis ought to make 

 the thing clearer, as it is very important, and 

 I am sure many others have the same difficulty 

 I have in harmonizing the article with one's 

 experiences and reasoning powers. 



Clarence L. Speyers 



CAMBErooE, Mass., 

 December 14, 1908 



MARS AS the abode OF LIFE' 



Although it is improbable that these lines 

 will be read by more than a small proportion 

 of those who have seen or heard of Mr. Perci- 

 val Lowell's " Mars as the Abode of Life," it 



* A series of lectures delivered before the Lowell 

 Institute, Boston; later published in the Century 

 Magazine, 1908; and subsequently issued as a 

 volume by the Macmillan Company, New York, 

 1908. 



seems worth while to point out to the scien- 

 tific workers of the country the gross errors 

 which this book is propagating. In this I 

 shall confine myseK to geological matters, 

 leaving the astronomical and other questions 

 to those who have special acquaintance with 

 such things. It is not surprising that Mr. 

 Lowell, an astronomer, should have only a 

 layman's knowledge of geology; but that he 

 should attempt to discuss critically the more 

 difficult problems of that science, without, as 

 his words show, any understanding of the great 

 recent progress in geology, is astonishing and 

 disastrous. One can not but recall the adage 

 that "fools rush in where angels fear to 

 tread." 



Mr. Lowell is an implicit believer in the 

 Laplacian theory of planetary evolution, a 

 hypothesis now on the defensive, to say the 

 least, and utterly abandoned by some of our 

 best cosmogonists. 



On an adjacent page he says that the min- 

 erals of the metamorphic rocks " show by their 

 crystalline form that they cooled from a once 

 molten state." The fallacy in this statement 

 is evident to the average college student of 

 geology or chemistry. Metamorphic rocks are 

 produced by processes which involve more or 

 less pressure and heat, but not melting. 



Turning to consider the evolution of life 

 on the earth, the author tells us that " the 

 geologic record proves that life originated in 

 the oceans. . . . Whether life might have gen- 

 erated on the land we do not know; on earth 

 it certainly did not." The truth is that the 

 geologic record proves nothing whatever about 

 the origin or even the infancy of life. It 

 may be fairly doubted whether it takes us 

 back even to the middle age of the animal 

 kingdom. Such a dogmatic assertion is, 

 therefore, wholly unjustified. In this con- 

 nection it is hard to resist pointing out that 

 among the oldest known fossils are certain 

 Eurypterids (Walcott's Beltina danai) which 

 are generally interpreted as fresh-water 

 rather than marine forms. 



Farther on we read, of the plants which 

 formed the Carboniferous coal beds, " Only a 

 warm, humid foothold and lambent air could 

 have given them such luxuriance and im- 



