284 



I cuuld not obtaii] it finer than sixty wirps to the inch, and in this 

 case I could obtain no indications of differences in the transmitted 

 ratios of one or other kind of heat. The proportion transmitted 

 to the direct effect, was, in every case, almost exactly that of the 

 area of the interstices of the gauze to its entire surface. 



" When fine gratings (used for Fraunhofer's interference fringes) 

 made of cotton-thread were used, even in this case no difference 

 was perceived ; here, however, the thread having probably a cer- 

 tain degree of permeability, might mask the effect. 



" When fine powders were strewed between salt plates, leaving 

 minute interstices, the easier transmission of heat of low tempera- 

 ture was again apparent. 



" Having procured delicate lines to be drawn with a diamond point 

 on a polished salt surface, first dividing it into squares 1-1 00th inch 

 in the side, then into parallel stripes l-'200th inch apart, and finally 

 into squares of the latter dimension, in every case the effect re- 

 sembled that of random scratches, and was made apparent as the 

 surface was more furrowed. 



" I have finally to observe, that the mere process of natural tar- 

 nishing by the exposure of salt to the air, produces a similar effect. 



" These facts evidently point to phenomena in heat, resembling 

 diffraction and periodic colours in light. I cannot doubt that the 

 simple transmission through fine metallic gratings, would produce 

 effects similar to those of the striated surfaces of rock-salt." 

 " December 16. 1839." 



2. On the Functions of the Roots of the Spinal Nerves in 

 corroboration of former observations, proving that the 

 anterior roots are nerves of motion, and the posterior 

 nerves of sensation. By Sir Charles Bell, K.H. 



The instance produced was a case which had occurred in the In- 

 firmary, in which the anterior roots of the nerves arising from the 

 Cauda equina were engaged in a tumour, and the consequence du- 

 ring life, was the loss of muscular power, sensibility remaining un- 

 affected. 



The following candidates were elected Fellows of the So- 

 ciety : — 



Alan Maconocbie, Esq. 

 Martyn J. Roberts, Esq. 

 Dr Daun. 



