257 



by the proboscis passes over these hairs, and communicates the 

 sensation of taste. He thought that the larger hairs were 

 tactile organs. 



Mr. E. F. Law exhibited a number of extremely interesting 

 lantern-slides. These were photomicrographs, taken on the 

 Lumiere autochrome plates, of the brilliant oxidisation colours 

 caused by heat-tinting on polished surfaces of various commercial 

 copper and iron alloys. Mr. Law said, in the course of his 

 remarks, that this heat-tinting is used as a means of dis- 

 tinguishing the constituents of an alloy. The tints are obtained 

 by the heating of a highly polished surface until it begins to 

 oxidise. To prevent further oxidisation, it is suddenly cooled by 

 plunging it into mercury. The different constituents of an alloy 

 oxidise at different rates, and each gives a different colour. The 

 magnifications employed were x 100 and x 1,000 diameters, and 

 were obtained by the use of a Zeiss vertical photomicrographic 

 apparatus with prism illuminator. With the illuminant used, 

 a powerful arc, the average exposure was half a minute for 1 ,000 

 diameters, and a very little less for the lower magnification. 

 The small difference is to be referred to the employment, in 

 the one case, of an oil-immersion objective. 



In moving a vote of thanks, the President made some very 

 appreciatory remarks on the success which had attended the 

 application by Mr. Law of the new processes of colour-photography 

 to metallurgy. 



Journ. Q,uekttt Microscopical Club, Ser. 2, Vol. X., No. 62., April 1908. 



