330 Proceedings of the British Association for 1850. 



Dr Anderson then announced the results of some important 

 observations on the action of nitric acid upon the vegetable 

 alkalis, which he is engaged in prosecuting. 



" On the Influence of Sunlight over the Action of the 

 dry Gases on Organic Colours," by Dr George Wilson. 

 The object of this communication was to report the result 

 of a series of experiments made this summer, on the effect 

 of daylight in modifying the chemical action of eight dif- 

 ferent dry gases, viz., chlorine, sulphurous acid, sulphu- 

 retted hydrogen, carbonic acid, a mixture of sulphurous 

 and carbonic acid, oxygen, hydrogen, and nitrogen on or- 

 ganic colouring matters. All of these gases were found to 

 act more powerfully in changing colours when exposed to 

 sunlight than when left in darkness. The effect was greatest 

 in the case of the bleaching gases, especially chlorine, which 

 the author shewed, may be left for three years in contact 

 with colouring matter without bleaching occurring, provided 

 moisture is excluded, whereas the same gas, though equally 

 dry, was found to bleach dry colouring matter in six weeks, if 

 exposed to sunshine, so that a fortnight of sunshine is more 

 than equal to a year of darkness in determining the decoloris- 

 ing action of dry chlorine. These researches are to be con- 

 tinued and extended at the request of the Chemical Section. 



Professor Williamson communicated a paper on the Theory 

 of Etherification, which excited much interest, and led to 

 considerable discussion. 



Section C. — Geology and Physical Geography. 



Robert Chambers, Esq., read a paper " On the Glacial 

 Phenomena around Edinburgh." The paper opened with a 

 description of the local phenomena, partly with a view to the 

 gratification of the strangers present on this occasion, who 

 might otherwise remain ignorant of them. Mr Chambers 

 described the Corstorphine Hill as a stratum of trap dipping 

 to the west, and with a cliff in a line north and south. In 

 its crest, which rises to 470 feet above the sea, are three or 

 four transverse clefts. On the west surface of the hill, the 

 rock, wherever it is exposed, is found to be rounded (nion- 



