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influence the amount of refraction ; yet few of the observations on 

 record have affixed to them the temperature at which they were 

 made, and few, if any, numerical researches have been published on 

 the subject. To determine, if possible, the amount and character of 

 this effect of heat was the object of the present inquiry. 



The instrument employed was that described by the Rev. Baden 

 Powell in the British Association Report for 1839, and was kindly 

 lent by him for the purpose. The substances more or less fully 

 examined, were bisulphide of carbon, water, ether, methylic, vinic, 

 amylic, and caprylic alcohols, the two principal constituents of 

 creasote hydrate of phenyle and hydrate of cresyle, phosphorus, oil 

 cassia, and camphor dissolved in alcohol. 



Of the tabulated results the following two will suffice to illustrate 

 the main conclusions : 



Bisulphide of Carbon. 



