1894.] 



on tlie Newtonian Constant of Gravitation. 



367 



Whitworth measuring machine. For this class of work sunshine or 

 dust give great trouble, but I was fortunate in Laving splendid weather 

 for my purpose, as visitors will probably remember : it rained without 

 ceasing during the two days I was making these measurements. 



Having now very imperfectly described the apparatus and the 

 place in which I have carried out my experiments, I will next show a 



Fig. G. 



series of photographs, which I took by magnesium light, to give a 

 better idea of the appearance of the apparatus and its surroundings. 

 Fig. 5 is a view of the vault showing the clock, the eye end of the 

 big telescope, and the little telescope. In the distant corner is seen 

 the felt screen with a long slit, through which the scale and telescope 

 can be seen from the mirror of the instrument. This, of course, is 



