Proceedings of the British Association. 271 



engaged in a series of experiments on the heat of the sun, as observed 

 by means of a thermo-electrical apparatus applied to an image of the 

 luminary thrown on a screen from a telescope in a dark room. He 

 found that the solar spots were perceptibly colder than the surround- 

 ing light surface. Prof. Henry also converted the same apparatus 

 into a telescope, by placing the thermo-pile in room of the eye-glass 

 of a reflecting telescope. The heat of the smallest cloud on the 

 verge of the horizon was instantaneously perceptible, and that of a 

 breeze four or five miles off could also be readily perceived. 



'On Fog-rings observed in America/ by Sir D. Brewster. — This 

 paper had been communicated to Sir D. Brewster by Sir John P. 

 Boileau, respecting a fog bow which had been seen in January, 1808, 

 by Sir George Rose, when off the Montgomery Reach, in the Poto- 

 mac, in Virginia. Early in the morning a milk-white fog came on, so 

 thick that the captain of the packet found it necessary to anchor, not 

 knowing where he was. About half-past eleven he came up to Sir 

 George, and remarked that they should have all clear soon, " for the 

 fog-eater was come." The captain explained himself by pointing to 

 the head of the vessel, where there was visible a ring of thicker white 

 fog than that in which they were enveloped, apparently about 60 feet 

 in diameter, the belt of the ring appearing about 2 feet broad. Within 

 this ring was another, 2 feet in diameter, suspended in its centre, and 

 with prismatic colours. It lasted about 20' or 30', when the fog 

 cleared away. There was a severe frost on the following day. 



' On a System of Numerical Notation, 5 by Mr. T. W. Hill.— This 

 was proposed to be founded upon the number 1 6, and those derived 

 from it by successive division by 2, — such as 8, 4, 2, 1 . By the com- 

 binations of these all numbers were to be formed, and by attaching 

 letters as the marks or names for the elementary numbers, a system 

 of nomenclature was obtained which seemed grotesque and cumbrous 

 in the earlier numbers, but which the author maintained became less 

 complicated in the large and ordinarily less manageable numbers. 



Saturday. 

 Section D.— ZOOLOGY AND BOTANY. 

 Dr. Carpenter read his Report ' On the Microscopic Structure of 

 Shells.' 



2 N 



