NATUIiAL PHILOSOPHY. 189 



to escape from an aperture in the bottom of the circular vessel containing it ; 

 if they will do so in the right spirit, I am fain to think they will arrive at the 

 same conclusion as the contemplation of this familiar phenomenon has brought 

 me to. 



OX THE ROTATION OF THE MOOX. 



One of the notable events connected with the progress of science during 

 the past year has been a discussion which has prevailed in England respecting 

 the question, " Does the moon revolve on her axis, or not ?" 



The question was first started by a London gentleman somewhat favorably 

 known for his literary, though not for his scientific attainments, by a commu- 

 nication in the London Times, in which he assumed the negative hi defiance 

 of all astronomers. He charged them with designating that a rotation which 

 is no rotation. The very fact which leads astronomers to impute to the moon 

 a rotary movement, was adduced as a proof that she does not rotate. He 

 argued thus: " If the moon turned at all on her axis, a little consideration 

 will show that all her surface would be successively shown to the earth, and 

 that it is because she has no rotary motion at all, that one side only is seen 

 by us. She performs precisely the same motion in relation to the earth, that 

 a point on the tire of a wheel does to the box or axle, or that the round end 

 of the minute-hand of a watch does to the pivot in the centre. It is easy to 

 construct a small instrument similar to this, by fixing a bah 1 on one end of a 

 strip of wood to represent the earth, and fastened by a pivot serving as its 

 axis, and on the other end a smaller ball, also fastened by a pivot. If the 

 strip of wood be turned round on its pivot at the end representing the earth, 

 the small ball will exactly represent the moon, and will present the same face, 

 through the whole of its revolution, to the large ball ; but if the small ball be 

 made to rotate on its. axis ever so little, it will immediately present a change 

 efface to the larger ball, and so would the moon to the earth." 



The charge was met by a great outburst of counter-ridicule and indignation. 

 A gentleman, who was an astronomer and a wag at the same time, said, 

 " I beg to inform him that I live in the moon, and that as I walk round the 

 earth hi order to keep my weather-eye open, so as continually to have it in 

 view, I am obliged to perform a rotation on my axis once a month. I tried 

 the other plan long ago, by always keeping my face to the north as I made 

 my rounds ; but then I turned in succession my face, my left side, my back, 

 and my right side to the earth. I soon, however, got a ' round robin' from the 

 earth, requesting me to go upon the old plan ; so I gave up the experiment." 

 Another advised the accuser thus: "Let him walk round a circular table, 

 with his face always turned towards its centre, and by observing that the 

 objects which originally appeared on his right, will appear, on the completion 

 of one half of his perambulations, to be on his left, he will probably be able to 

 convince himself that he has been turning round a vertical axis." 



But as the accuser refused to be beaten down by ridicule, numerous prac- 

 tical illustrations were suggested to his attention; some of which may be 

 usefully transcribed. 



1. " Suppose that a mariner's compass is fixed on the edge of a wheel 



