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On a new Form of the Differential Thermometer, with some of its Ap- 

 plications. By William Ritchie, A.M. Rector of Tain Academy. 

 Communicated by J. F. W. Herschel, Esq. Sec. R.S. Read De- 

 cember 21, 1826. [Phil. Trans. 1827, p. 129.] 



The instrument described by Mr. Ritchie in this paper, consists of 

 two hollow cylinders of tin-plate, of large diameters in proportion to 

 their height, placed with their bases parallel to each other, and at a 

 moderate distance, and connected by a glass thermometer-tube, con- 

 taining a coloured liquid, and in the form of an inverted syphon, 

 after the manner of the photometer described by the same author in 

 the Philosophical Transactions for last year. This instrument being 

 placed between two sources of radiant heat, at such distances that 

 the coloured liquid shall remain stationary in the tube, fixes the 

 distances of equal radiation, from whence the radiations at equal di- 

 stances may be calculated, supposing the law of the decrease of heat 

 by radiation known, and vice versd, supposing the ratio of the heats 

 radiated at equal distances known, the law of radiation may be ex- 

 perimentally investigated. 



As instances of the application of this instrument to experimen- 

 tal purposes, the author relates several experiments on iron balls, 

 equally heated, and exposed at such distances as to subtend equal 

 apparent diameters at the faces of the cylinders. From these he 

 concludes that the law of the decrease of heat, as the inverse squares 

 of the distances, is founded in fact. When, however, the heated 

 bodies exposed had flat surfaces corresponding to those of the sur- 

 faces of the cylinders, he found a less rapid law of decrease to hold 

 good ; from which he concludes, that a constant portion of heat is 

 radiated directly out from the surface without divergence, because 

 an equal quantity, added to both terms of a ratio of greater inequa- 

 lity, as is well known, diminishes the ratio. 



On the Structure and Use of the Submaxillary Odoriferous Gland in 

 the Genus Crocodilus. By Thomas Bell, Esq. F.L.S. G.S. Com- 

 municated by Sir Everard Home, Bart. V.P.R.S. Read March 1, 

 1827. [Phil. Trans. 1827, p. 132.] 



The author begins by remarking on the general inattention pre- 

 vailing among anatomists, to such glands as produce anomalous se- 

 cretions, required only by the peculiar and exclusive habits of the 

 animals possessing them. A gland of this kind subsists beneath the 

 lower jaw of the alligator and crocodile. It is situated on each side, 

 and secretes an unctuous substance of a strong musky odour. 

 Neither its structure nor its probable object have yet been considered 

 with any care, till the author, about two years ago, discovered in it a 

 structure which he thinks is without a parallel in the glandular system 

 of other animals. His observations were made on the common alligator 

 of America. In this animal the external orifice of the gland is situated 



