10 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



graduate leaks apart from the still in such a manner that the tension 

 could be held constant for some time at any desired point. 



The accompanying figure represents the form of regulator that has 

 been used in all our distillations of large as well as small quantities of 

 oils, together with the complete apparatus in the form for use. The 

 regulator consists simply of a glass stopcock, A, better of considerable 

 size, attached to the manometer by means of a side tube. To regu- 

 late closely the inflow of air an arm three to five feet in length, 



according to the working of the stopcock, is attached firmly to the 

 head of the cock, and supported in a manner easily movable within 

 very small divisions on the arc of a circle of which it is the radius. 

 To enable the operator to make adjustments while standing in front of 

 the manometer, a piece of lead is attached as a weight to the upper 

 end of the lever, and a cord is carried over a pulley, B, and terminates 

 in a ring in front of transverse rows of pins a few millimeters apart. 

 For economy of space the pulley is placed lower in the figure than its 

 actual position. The upper part of the lever consists of two strips of 

 wood, with a space between, through which passes a rigid copper wire 

 as a support and guide. With the lever in a vertical position, the 



