British ^Association for the Advancement of Science. 475 



pelling elastic fluids from his fine linseed oil barometer. Dr. 

 Brewster exhibited alum and rock salt prisms, excelling the 

 finest glass prisms. This adaptation of cheap substances to such 

 a purpose, produced some explanation as to Dr. Brewster's views 

 of the heating rays of Herschell, supposed to be most numerous 

 in the dark part of the spectrum, where he found the tempera- 

 ture highest Dr. Brewster is of opinion, that there are no rays 

 of heat unaccompanied by light. — Colouring matters also were 

 treated upon. It was argued, that where a mixture of bodies 

 has changed the colour of both or either, it is not that the one 

 has penetrated into the other, so as to impart its colour to it, 

 hut that the union of the two has taken place in such a manner, 

 as to produce an arrangement of the particles, which causes the 

 light to be reflected in a particular way. — Mr. Forbes then re^d 

 an elaborate paper, on the horary oscillations of the barometer. 

 The morning closed by a communication from Sir .Tames South 

 to Dr. Brewster ; he had lately observed one of the satellites of 

 Jupiter, which were generally supposed to disappear, when with- 

 in the disc of the planet, to appear as a black spot on its surface. 

 He was desirous of having this anomaly accounted for. 



• In the evening. Dr. Daubeny explained some experiments of 

 the Rev. Mr. Taylor, of York, with a view to increase the inten- 

 sity of gas light, without increasing the consumption of gas. The 

 Rev. Mr. V. Harcourt also explained the principle of a new 

 tamp, invented by him, for the purpose of economising light, by 

 the use of cheaper oils. An able memoir by Brewster, was then 

 read, " On a JYew A?ialysis of Solar Light.'''' The last paper read, 

 was a translation of a memoir, by Professor Gazzeri, of Florence, 



On a method of rendering visible the traces of erased writing." 

 This consisted mainly in the application of heat. Dr. Brewster 

 mentioned, that the legends of worn out coins and medals, when 

 placed on hot iron, would evolve in like manner. He had been 

 much surprised, at first reading on such a medal, in letters in 

 •flame, the legend, " Benedictum sit nomen Dei.^^ 



Lord Morpeth now addressed the meeting, and moved thanks 

 to Dr. Brewster ; when the unbounded applause had subsided 

 w^hich his eloquent speech produced, 



Mr. Murchison, on the part of Dr. Brewster and his other scientific friends, 

 begged leave to return thanks for the high honour done to the contributors 

 £)f.scientific memoirs, and for the kind assistance and valuable aid which had 



