Proceedings of the British Association. 117 



proceed with their similar poles similarly arranged as at first, but 

 interference of media might be conceived, which, by deranging the 

 relative positions of the poles, or the particles of beams of light, 

 moved so as to give the rays new physical characters. But he had 

 not meant at all, when mentioning this view, to intimate that he had 

 any settled opinion that a theory could be worked out for this or any 

 other such view, by any means as complete as the undulatory 

 theory. 



A Thermometer Stand, by Mr. Lawson, and used at his Meteorolo- 

 gical Observatory at Bath, was then described, ' The Meteorological 

 Thermometer Stand' was stated to possess the following requisites : 

 It can be placed on any eligible spot. Its four sides can and must 

 be placed to face the cardinal points ; commanding, therefore, a true 

 north and south aspect. It can be visited on every side, and be free 

 from all surrounding objects. The instruments or thermometers used, 

 can be read off with great facility ; and the whole will be at a known 

 distance from the ground. Those instruments placed on the south 

 face will have the meridian sun ; and those on the north face will be 

 always in the shade, in consequence of the projecting wings. It can 

 be employed by any meteorologist wherever residing. It is of a 

 determinate form, height and size. It is not costly, and may be con- 

 structed by any intelligent carpenter. It can be placed in any open 

 situation. By the general adoption of this stand, instruments placed 

 upon it will be all observed under similar circumstances, and can be 

 compared with far less chance of error, than has hitherto been the 

 case. — A model was exhibited, and a working plan and description 

 distributed. 



Dr. Lee bore testimony to the value and simplicity of the stand. 



Section B.— CHEMISTRY AND MINERALOGY. 



'On the ActinograpV by Mr. Robert Hunt. — After referring 

 to Daguerre's statement that the solar light, two or three hours 

 before noon, was different in its chemical character from that 

 which proceeded from the sun at equal times after it had cross- 

 ed the meridian, the author proceeded to state from his own 



