Geological Society, 233 



ively, would appear to be the same, the relative thermometric effect 

 for these disks varying inversely as their thickness, and being in the 

 following proportions, 30, 43, CO, as determined by one complete set 

 of experiments. 



Again, the quantity of heat developed in the thick aluminium disk, 

 with its surfaces both un coated, was probably the same as when one 

 surface was coated and one left bare, or as when both surfaces were 

 coated. 



25. The authors will not attempt here a further generalization, 

 but they would desire to make one remark. In absence of definite 

 knowledge of the nature of that medium which transmits radiant 

 light and heat, it might be supposed possible that when a radiant 

 body is in rapid motion, the intensity of its radiation is somewhat 

 increased. But if we bear in mind that in these experiments the 

 effect was observed after bringing the disk to rest, and that the 

 temporary effect during rotation sometimes observed can probably 

 be otherwise accounted for, we are forced to conclude that, as far 

 as we may judge from these experiments (and tKey are of a very 

 delicate nature), there is no perceptible effect of motion upon radi- 

 ation. 



In conclusion the authors desire to say that they are much in- 

 debted to Mr. Beckley, who not only invented the apparatus, but 

 assisted at all the experiments, and without whom they could not 

 have been performed in a manner so satisfactory. They are also in- 

 debted to Mr. Atkinson for his kindness in lending them a large 

 gasometer, and to Mr. Browning and Mr. Ladd for exceedingly true 

 aluminium and ebonite disks. 



GEOLOGICAL SOCIETY. 



[Continued from p. 154.] 



January 9, 1867.— Warington W. Smyth, Esq., M.A., F.R.S., 

 President, in the Chair. 



The following communication was read : — 



" On the age of the Lower Brick -earths of the Thames Valley." 

 By W. Boyd Dawkins, M.A. (Oxon.), F.G.S. 



The Lower Brick-earths of the Thames Valley have been a fertile 

 source of discussion since the year 1836, — Dr. Falconer considering 

 them to be anterior in age to the Boulder-clay, Mr. Prestwich be- 

 lieving them to belong to the Low-level series of Quaternary de- 

 posits. The author divides the evidence upon this question into 

 two heads — Physical and Palseontological. The sections at Ilford, 

 Grays, Thurrock, Crayford, and Erith evince the same sequence of 

 deposits. At the bottom of all are the fluviatile Brick-earths and 

 Gravels, whence the Mollusca and Mammalia are derived, and which 

 are remarkable for the horizontality of their bedding and the even 

 sorting of the component parts. Lying on the eroded top of these 

 is a deposit (the trail of Mr. Fisher) of a highly confused nature, 



