"16 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The machine may be said to consist of three portions— the motion, 

 the bearing spindle, and the disc. The motion is enclosed in a metal 

 box, which is filled up with oil, so that the gearing wheels are running 

 in a regular oil-bath. It consists of one pair of spur-wheels and a pair 

 of screw-wheels, Avhich transmit movement to the upright spindle 

 through a smaller wheel, and the gearing is so arranged that one revolu- 

 tion of the driving wheel — corresponding, of course, to one revolution 

 of the handle — is equivalent, in round numbers, to 50 revolutions 



Fig. 164. 



the bearing spindle, so that 40 turns of the handle per minute "ive a 

 speed of about 2000 revolutions of the disc in the same time, and the 

 labour involved in producing this speed is well within the powers of 

 the ordinary laboratory boy. 



The handle is attached to the spindle of the driving wheel by means 

 of a short Screw with a quick thread, so that, on ceasing to turn the 

 handle and holding it steady, two or three revolutions of the driving 

 spindle completely unship the handle and leave it free in the hand. 



The upright spindle is surmounted by a gun-metal cup containing 

 a cone-shaped block of vulcanised rubber, renewable at will, upon which 



