358 Proceedings of the British Association. * 



earth, and the experiments and observations by which its exist- 

 ence was placed beyond doubt 5 and the law of its distribution, 

 as it ascended to the surface, traced ; and he stated, that the 

 issue from the surface at each part was so much in a century as 

 would be capable of melting three metres of ice heaped upon 

 that surface. He then discussed the subject of cosmical heat — 

 and showed the probability that the regions of space were not 

 of a uniform temperature ; hence he concluded, that all the bo- 

 dies of the solar system had a tendency to acquire the tempera- 

 ture of that part of space in which they are placed, and that the 

 heat of the planetary spaces was only about 50° below the freez- 

 ing point. 



8. Dr Allman, Professor of Botany, next read a very inter- 

 esting paper on a mathematical inquiry into the forms of the cells 

 of plants. His views were illustrated by specimens of plants, as 

 well as by models of the geometrical solids ; to us, one of the 

 most interesting portions of this ingenious communication was 

 that part in which he developed the mutual relations of the five 

 solid forms, which, taken two and two, he denominated recipro- 

 cal solids, or such as, by slicing off the angles of one, would 

 lead to the bounding planes of the other. Thus, the tetrahe- 

 dron is reciprocal to the tetrahedron alone, for the angles being 

 equally sliced off, you will, by the slicing planes, be led to an- 

 other body, contained by the three slicing or truncating trian- 

 gular planes — the angles of the reciprocal corresponding to the 

 sides of that to- which it is reciprocal. The cube and the octo- 

 hedron he also showed to be reciprocal ; and, lastly, the dode- 

 cahedron and icosahedron. This was the only part of the paper 

 which came properly under the consideration of the Mathemati- 

 cal and Physical Section. The other very curious and interest- 

 ing observations on the effect of compression in determining the 

 forms of the cells of plants, were considered as rather coming 

 within the province of the botanist and physiologist than of the 

 mathematician ; and, as much business yet remained for the 

 day, Dr Allman, at the request of the President, contented him- 

 self with stating some general views in conclusion, 



9. Dr Reid, of Edinburgh, read a paper upon Sound, par- 

 ticularly in relation to the precautions necessary to be attend- 



