62 REPORT— 1839. 



which, though existing in the same plant, and procured by the same 

 process, present marked distinctions. 



The one, being of lower specific gravity than the water, floated upon 

 the surface of that which distilled along with it ; while the other, 

 being considerably heavier, sunk to the bottom of the receiver. Both, 

 when fresh, were transparent and colourless ; but in a few days they 

 changed to a yellow colour, the heavier assuming a deeper tinge than 

 the other. 



In smell the oils differ perceptibly, that of the heavier being fatty 

 and unpleasant, while the odour of the lighter is aromatic and agree- 

 able. In taste they are equally acrid and disagreeable. The specific 

 gravity of the lighter oil is 0-949, that of the heavier 1*028, both 

 having been examined several days after their preparation. Upon 

 exposing them to a temperature of 18° Fahr., no effect was produced 

 upon the lighter oil; but in the heavier a great quantity of sparkling 

 needle-shaped crystals were observed, which, however, speedily dis- 

 solved upon the phial being removed out of the freezing mixture. 

 The mineral acids rapidly decompose them, converting both oils into 

 fluids of a deep red colour. 



In a chemical point of view the oils referred to are interesting, 

 upon account of their presenting such marked distinctions in colour, 

 smell, specific gravity, and the effect of cold upon them, although they 

 are the produce of the same plant. 



On an improved method of graduating Glass Tubes for Endiometrical 

 purposes. By Charles Thornton Coathupe. 



The instrument employed by Mr. Coathupe for this purpose consists 

 of a truly-bored cylindrical tube of iron, into which an iron piston is 

 accurately fitted. Upon the rod of the piston a screw was cut with 

 a good pair of dies, throughout its entire length. The rod is then 

 filed into a triangular form, leaving a sufficiency of the threads of the 

 screw at the rounded angles for an iron nut to traverse with security 

 and freedom. 



To the upper extremity of this iron cylinder a cap of the same metal 

 is screwed, and into this cap is screwed an iron stop-cock: to the stop- 

 cock is attached a glass measure, with a narrow lip, by means of an iron 

 connecting socket. 



Near the opposite extremity of the cylinder an iron diaphragm, of 

 about a quarter of an inch in thickness, is inserted, and is fastened in 

 its place by a side screw or pin, and through this diaphragm a trian- 

 gular-shaped hole is made, through which the piston rod can slide 

 easily up and down, but without lateral shake. 



Below the diaphragm, and at the extremity of the cylinder, the nut 

 is inserted, whose action propels or retracts the piston, without the pos- 

 sibility of the piston itself deviating from a right line. 



This nut enters the cylinder to the depth of about half an inch, and 

 around the entering part a deep V-shaped groove is turned, into which 

 the pointed ends of three steel screws enter through the exterior of the 



