and Laboratory Methods. 



1449 



lenses. The lens on the tip may be removed, thereby rendering the remaining lens 

 lighter to hold in the eye, while at the same time giving sufficient amplification for 

 most work. The great advantage of this magnifier is that both hands are free, 

 and the object can be placed or held up in the most favorable light. The 

 objection to its use is that a considerable portion of the students, despite the 

 most careful directions and praiseworthy perseverance on their part, are unable 

 to retain the magnifier on the eye. This year I have had a detachable spring 

 added to the mounting. This is a heavy watch spring which goes round the 

 head and when properly adjusted holds the lens comfortably in a suitable posi- 

 tion. Even those who can hold the lens on without the spring find that when 

 the protracted use of the instrument is necessary fatigue is reduced to a minimum 

 or eliminated by using the spring. The latter's being detachable permits the 

 glass to be carried in the pocket and used in the hand for simple magnification 

 as conveniently as a folding lens. The spring is kept with the kit of dissecting 

 tools and attached when desirable. Its use so far is proving highly satisfactory. 

 London Normal School, London, Canada. J. DearNESS. 



A New Thermo-Regulator. 



The following is a simple and extremely efficacious form of thermo-regulator 

 which was shown to me some while ago by one of my ingenious friends, and 

 who kindly undertook to provide me with one. I have been trying it on an air 

 sterilizer (one of Jung's) with the 

 most satisfactory results. I have 

 also got one for low temperatures, 

 as per modifications suggested by 

 myself : i e, India rubber cork 

 through which passes the tube t, 

 at the inner end of which is a coni- 

 cal entrance, c. B is a glass float 

 which is counterpoised, and which 

 either rises so as to obstruct the 

 gas entry (the black end closing 

 the tube t), or it descends into the 

 cup A. This cup is provided with 

 a tube which dips into the mercury. 

 The apparatus being put into its 

 place, the heat causes the mercury 

 to rise into the cup A, and lifts B, 

 which will finally, i e., at a given 

 temperature, obstruct the gas pas- 

 sage so as to limit the supply of 

 gas, and thereby govern the tem- 

 perature. 



The form shown is, of course, serviceable for only one temperature, but 

 by interposing a metallic cap and screw, as shown in the left figure, acting on a 

 leather diaphragm, the apparatus may be regulated to any temperature. 



Thos. Pal.mer. 



