604 EEPORT — 1881. 



not precipitated hj ammonia m presence of ammoniacal salts. It is a permanent 

 white, witli a slight salmon-colour tinge ; calcined, the tint is similar. It does not 

 change colour by exposure to the air, neither does it appear to be affected by sun- 

 light. It is readily soluble in acids. 



Sulphide of Actinium. — The hydi-ate, as precipitated from its neutral or alkaline 

 solutions by sulphide of ammonium, is a bulky, pale, canary-yellow precipitate ; 

 insoluble in excess of sulphide of ammonium, very slightly soluble in acetic acid, 

 readily soluble in mineral acids, even when rather dilute. Exposed to the direct 

 rays of the sun it darkens in about twenty minutes, except where protected by a 

 piece of glass. 



12. On BowJcett's Thermograph. 

 By Wm. Lant Cakpenter, B.A., B.Sc, F.G.S. 



The construction of this instrument is based on an application of the principle of 

 Bourdon's steam-gauge, the changing pressure of a confined fluid under varying 

 temperatures being used to obtain a motion for registering those temperatures. 

 Upon a flat, circiilar, metallic vessel, 3 inches in diameter and |-inch thick, is a 

 hollow metallic spring or sealed tube communicating with it, filled with fluid, 

 circular in shape, and fixed at one end. The other end is free to move, and very 

 minute changes in temperature cause it to do so, the amount of movement being 

 proportionate to the pressure, and this again proportional to the increase of tempe- 

 rature producing the expansion. The movements are magnified by a lever system, 

 and recorded by a pen upon a cardboard disc, rotating once in twenty-foiu" hours, 

 divided by concentric circles into degrees, and into hours by radial lines. The 

 instrument had been extensively used, clinically and otherwise, and would be 

 useful in the laboratory for recording purposes, where a prolonged constant tempe- 

 rature was necessary. 



