Royal Ifistitution of Great Britain. 307 



FRIDAY-EVENING PROCEEDINGS AT THE ROYAL INSTITUTION 

 OF GREAT BRITAIN. 

 Feb. 27. Mr. Faraday gave an account of Brard's test of the ac- 

 tion of weather on building materials. He prefaced his particular 

 account of the test proposed, by a general view of the actions that 

 go on in these climates upon the building materials ordinarily in 

 use. The actions were considered as of two kinds, chemical and 

 mechanical ; instances of both were referred to and exhibited : the 

 former were stated to produce more good than harm, but the latter 

 to be decidedly and seriously injurious. The mechanical actions 

 are of different kinds, but the action of water and frost are the most 

 powerful : all of them are fully met by the proposed test, which 

 consists in boiling prepared specimens of the materials to be tried 

 in a solution of sulphate of soda, and then suspending them in the 

 air and allowing evaporation to proceed until the salt crystallizes : 

 by dipping the specimens into a cold saturated solution, and again 

 causing crystallization to take place, an exact imitation of the 

 effects of frost is produced. Mr. Faraday stated, that he had ap- 

 plied M. Brard's test soon after his first publication of it, and could 

 bear testimony to its value. He said, that more lately it had been 

 minutely applied and regulated in France, and was there also re- 

 ceived with approbation. The mode of procedure was illustrated 

 by specimens in progress. 



Numerous specimens of Hindu and other sculpture were in the 

 Library, illustrative of the effects of weathering. 



March 6.— Mr. Brande gave an experimental development of 

 Mr. Hennel's late experiments and discoveries relative to aetherifica- 

 tion, and the nature of the substances produced by the action of al- 

 cohol and sulphuric acid. He more particularly illustrated Mr. 

 Hennel's new view, that the sulphovinic acid is probably a necessary 

 intermediate state in the production of aether. These researches have 

 been published in two papers in the Philosophical Transactions, the 

 first of which will also be found in Phil. Mag. vol. liv. p. 354'. 



March 13. — Mr. Brockedon on a new mode of sketching effects 

 rapidly in chiaro-oscuro, and its application in lithography. This 

 mode consists in applying the mezzotinto process either upon card- 

 board or lithographic stone. After applying a uniform coat of 

 black paint, or a mixture of lamp-black and pomatum, to card-board, 

 the lights are.taken out with a palette-knife, the finger, or any other 

 convenient tool, and with more or less breadth, at pleasure. The 

 same process applied on lithographic stone may be made to afford 

 very fine texture and beautiful effects. It has been practised in Ger- 

 many, France, and in this country, and numerous progressive spe- 

 cimens of the results were shown and referred-to. 



March 20.— Mr. Ainger's development of the origin and early 

 history of the steam-engine. Mr. Ainger's object was by a chrono- 

 logical arrangement of diagrams, faithfully representing the contri- 

 vances which at various periods have been proposed or executed to 

 render steam an active and useful agent, and by the comparison of 



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