140 VOLUMETRIC AND INDIRECT ESTIMATION OF FAT. 



the under disc-plate gently with the finger till it stops. Do 

 not stop it with a jerk. 



II, The "Excelsior" Gearing. This can be fitted to 

 8- or 24-sample machines. It consists of a hollow cylinder 

 fixed to the frame carrying a hollow double pulley, inside which 

 the spindle can rotate without touching. Round the lower 

 portion of the pulley is coiled a spring, and in the opposite direc- 

 tion round the upper a strap is wound, which passes through an 

 opening in the cylinder ; on thp strap is clamped a stop-plate, 

 which serves a double purpose (1) to prevent the spring from 

 pulling the strap too far, and (2) to lift the pulley, which is capable 

 of a slight vertical movement, when the strap is wound home. 

 At the bottom of the pulley is a pawl, which, when the stop- 

 plate is pulled out, engages a ratchet wheel on the spindle and 

 which is lifted with the pulley when the stop-plate is home, 

 so that the pulley runs freely. The machine is rotated by pulling 

 the handle on the end of the strap rapidly to and fro fifteen to 

 twenty times, when a high velocity is obtained ; the strap and 

 stop-plate are then allowed to go home and the machine runs 

 alone. If the speed slackens, it can be increased by a few further 

 pulls. This gearing is only recommended for 24-sample machines. 



III. The " Rapid " Gearing. In this, a loose pulley sur- 

 rounds the spindle ; it runs on a separate bearing and is, when 

 not in use, kept up by a spring. A strap passes round the loose 

 pulley, and when this is pulled (in a slightly downward direction) 

 the pulley is brought downwards ; two bevelled teeth engage two 

 similar teeth on the spindle and cause the machine to rotate. 



When the strap is pulled back (in a slightly upward direction) 

 the spring forces the pulley up and the machine rotates freely, 

 By pulling the strap rapidly backwards and forwards, a high 

 rate of speed can be obtained. 



The 2-bottle machine differs in construction from the others 

 in not having the disc-plates, which are replaced by two arms, 

 carrying cups ; these cups are larger than the cups used in the 

 larger machine and have a cover ; the test bottles fit completely 

 into them and are surrounded by warm water. 



The machine is fitted with the " Rapid " gearing, and has 

 plain bearings ; this causes continual driving to be necessary. 

 The machines cannot be left to run alone. 



None of the methods of driving the Gaertner-Hugershoff 

 machine are satisfactory. The catgut requires a strong pull 

 and is liable soon to wear out, if the metal end comes off ; if it 

 is required to rotate a second, time, the machine must be stopped. 



The " Excelsior " gearing has a weak point in the spring, 

 which breaks and is difficult to repair ; the strap also sometimes 

 breaks, and cannot be replaced without some trouble. 



