ANOMALOUS BEHAVIOUK OF DELICATE BALANCES, ETC. 



407 



Of the Method adopted for Maintaining Uniformity in the Temperature of the Air 



immediately surrounding the Beam. 



An attempt was now made to devise some method for avoiding fluctuations in the 

 temperature of the air in the neighbourhood of the beam. Upon reflection it 

 appeared highly probable that the greatest measure of success would be attained by 

 (l) greatly reducing the air space surrounding the beam, and (2) enclosing the beam 

 within a chamber consisting of materials capable of readily absorbing, reflecting, and 

 distributing any heat radiations which, under the usual conditions, enter the beam 

 and so become responsible for some of the errors to which attention has been directed. 



Fey. X. 



Now the researches of DE LA ROCHE, MELLONI, and others show that the most 

 suitable materials for this purpose are glass, well-dried wood, and metals ; and of all 

 metals aluminium possesses in the most marked degree those characteristics that we 

 most desire, namely, lightness, rigidity, great reflecting power, and high conductivity 

 for heat. 



