224 



Mr. K. H. M. Bosanquet on the 



tion of mechanical equivalents, I employ a 30-light gas-meter, 

 through which the wind passes on its way from the bellows. 

 This is connected with one of the largest slide-holes by means 

 of a large indiarubber tube and boxwood connexions. In this 

 way the wind used can be measured with considerable accuracy. 

 Electromagnetic Dial. — When the gas- and water-pipes were 

 laid down, I took the opportunity to have a couple of electric 

 wires, covered with gutta-percha, laid from my rooms to the 

 laboratory. The object of this was to make a connexion from 

 an excellent astronomical clock, which I possess, to the labo- 

 ratory. I tried first a modification of a method recently ap- 

 plied at Greenwich, according to which light steel springs are 

 acted on by a wheel on the spindle of the scape-wheel. I tried 

 the employment of springs in connexion with the scape-wheel 

 itself. This method proved an entire failure, owing to the 

 tendency which the springs possessed to "hang up." I could 

 not understand this for a long time, and thought that possibly 

 magnetism might be involved ; but it turned out to be only a 

 property of the particular steel employed, which "buckled" 

 occasionally, and set itself in its displaced position instead of 

 returning to its proper position of rest. Eventually I adopted 

 the following plan, which has proved so successful that it 

 leaves nothing to be desired. 



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A is the pendulum-rod. 



BCDEa wood frame, embracing the rod tightly at the 

 middle of C D, and having its top bar B E above the suspen- 

 sion of the pendulum. 



The bar BE carries at its extremities two brass plates 

 arranged as shown, both kept in communication with the 

 return-circuit by means of the wire F. Two large gun-metal 

 screws are carried in these brass plates, having stout platinum 

 wires inserted into holes drilled in their axes. From the clock- 



