XVII. On the influence of temperature on the refraction of light

Those who have occupied themselves with the determination of refractive indices, must have noticed that changes of temperature 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.