73 4 THE POPULAR SCIENCE MONTHLY. 



is much the same as that which would be formed by winding string 

 through and through a curtain-ring until it was full. It is probable 

 that the momentum of these rings corresponds very nearly with that 

 of the drops before impact, so that when rain is falling on to water 

 there is as much motion immediately beneath the surface as above 

 it, only the drops, so to speak, are much larger, and their motion is 

 slower. Besides the splash, therefore, and surface-effect which the 

 drops produce, they cause the water at the surface rapidly to change 

 places with that at some distance below. Such a transposition of 

 water from one place to another must tend to destroy wave-motion. 

 This may be seen as follows : Imagine a layer of water adjacent to 

 the surface, and a few inches thick, to be flowing in any direction over 

 the lower water, which is to be supposed at rest. The effect of a drop 

 would be to knock some of the moving water into that which is at 

 rest, and a corresponding quantity of water would have to rise up 

 into the moving layer, so that the upper layer would lose its motion 

 by communicating it to the water below. Now, when the surface of 

 water is disturbed by waves, besides the vertical motion the particles 

 move backward and forward in an horizontal direction, and this mo- 

 tion diminishes as we proceed downward from the surface. There- 

 fore, in this case, the effect of rain-drops will be the same as in the 

 case considered above, namely, to convey the motion which belongs 

 to the water at the surface down into the lower water, where it has 

 no effect so far as the waves are concerned, and hence the rain would 

 diminish the motion at the surface, which is essential to the contin- 

 uance of the waves, and thus destroy the waves. Nature. 



-- 



SCIENCE FKOM THE PULPIT. 



By JOHN TROWBRIDGE, 



ASSISTANT PBOFESSOB OF PHYSICS IS HABVABD TNIVEESITY. 



ARE ministers fitted to discuss the bearing of modern science 

 upon religion ? This question forces itself upon one who is 

 both a member of a church and a lover of science, and deserves to be 

 carefully weighed by those who have the interests of Christianity at 

 heart. An article by the editor of the Nation, in the issue of Decem- 

 ber 24, 1874, takes the very sensible ground that a man of science 

 should have no greater authority in controverted religious questions 

 than the most humble member of a church. His views are not enti- 

 tled to great consideration simply because he is a student of science. 

 This seems to touch the vital part of the question. The history of the 

 world shows, however, that the assumption of exclusive right to treat 

 religious questions with authority, and the barring out of critical in- 



