6o On Vegetable and Animal Analysis, 



side of the bell -metal circle, are fitted to each other with 

 the utinost accuracy, and great care taken to turn the said 

 tTuly fitting concentric with the axis of the circle; the brass 

 rings a and h are held together by twenty- four screws, as 

 ^hown in the plan ; and a groove, corresponding to the cur- 

 vature of the screw which moves the circle, is turned in the 

 outside of the two: in this state the racking of the teeth is 

 }5erfornied by a screw similar to that afterwards used to turn 

 the circle to its divisions, but notched across the threads so 

 that it cuts like a saw, when pressed against the circle and 

 turned round, and removes the metal from the spaces be- 

 tween the teeth, which are by this means formed around 

 the edge of the circle; when this has been performed all 

 round, two fine line.-^ are drawn across the brass and bell- 

 inetal circles, diameirically opposite each other ; the twenty- 

 four screws are then withdrawn, and the upper brass ring 

 turned exactly half round, which is determined by the lines 

 before mentioned ; and by this means tlie teeth of the cir- 

 cle are divided into two thicknesses, and being put together 

 again in opposite direction*, if anv error arose in racking 

 the teeth, it would be shown bv the upper and lower halves 

 of the teeth not coinciding when reversed, and. by racking 

 them while reversed the screw would cut away the incquali- 

 iies, and make all the teeth of the same size and distance 

 from each other : this reversing the teeth is performed se- 

 veral times, till the teeth are brought to a perfect equality 

 in ail parts of the circle; four steady pins are accurately 

 fitted into the two rings to hold them tugether in any of the 

 positions in which they have been racked together, and it is 

 upon these the dependence is placed for the coincidence of 

 the teeth, the twenty-four screws being nierelv to hold them 

 last together, and fitted rather loosely in their holes, that 

 they may not strain the steady pins. 



XIII. Extract from a Memo/r on Fegeiahle and Animal 

 Anali/iis. B/j MM. Gav-Lussac and Thknard. 



Bead at the Institute loth January, IS 10*. 



When we had conceived the project of analysing animal 

 and vcaelabie matters, the lirsl consideration which pre- 

 sented itself to our serious a'tenlion was to tiansform, by 

 means of oxvsen, the vegetable and animal substances into 

 water, carbumc acid, and azote. It was -evident that if we 



• AiirMla, dc Chimie, tovc.t kxiv, p. 47. 



could 



