Proceedings of the British Association. 125 



some little time, brass will be liberated on the cathode. The solution 

 is now ready for use, and is operated upon by two or three DanielPs 

 cells, and with a brass anode. By similar means alloys of gold and 

 copper, or gold and silver, may be deposited. The author reasons, 

 that true brass is a definite chemical compound; and states — It 

 appears possible that the anode, which is a brass of commerce, is a 

 true alloy, plus an excess of zinc ; that the solution it produces is a 

 mixed solution, which consists of the potassio-cyanide of brass and 

 the potassio-cyanide of zinc. This solution is very readily decom- 

 posable; it is therefore necessary to prepare it a short time pre- 

 viously to its use. Many specimens were exhibited of copper and 

 other metals coated with brass. The author makes some remarks 

 on the theory of the action ; and concludes by stating that it will be 

 quite possible to determine, within certain limits, the character of the 

 alloy that shall present itself, and that we may be enabled to throw 

 down gold and silver according to standard. 



Dr. Lyon Playfair read a paper on Atomic Volumes, of which we 

 have already given a report in our notice of the Chemical Society 

 [see ante, p. 591.] 



Thursday. 

 Section C.— GEOLOGY. 



f On the Geology of the Vicinity of Cambridge/ by the President. 



Prof. Sedgwick commenced by pointing out, on a geological map, 

 the general direction of the oolitic and cretaceous formations of Cam- 

 bridgeshire and the adjoining countries. He then proceeded to des- 

 cribe their subdivision and fossil remains,, commencing with the 

 chalk, which forms an elevated tract eastward of the Bedford Level, 

 ©ccasionally swelling into low hills such as those of Gog and Magog, 

 and containing a variety of fossils, especially at Cherry Hinton. Below 

 these hills commences a flat country stretching westward for many 

 miles, forming extensive tracts of marsh land and peat bogs ; a portion 

 of this nearest the chalk, and slightly swelling above the dead level of 

 the country beyond it, is occupied by the gault clay, which may 

 be seen in the pits near the Castle, and is met with beneath the 

 chalk, wherever that formation has been sunk through. South of 

 Cambridge it occupies a bay in the outline of the chalk district, in 



