On Numerical Proportions in Chemical Combinations. 109 



Pond Muscles but much smaller ? and to which particular stra- 

 tum or strata in Mr. Forster's Section, they belong. 



In the same work I observe it mentioned, that Professor Hail- 

 stone, of Cambridge, has presented to the Geological Society 

 an account of Fossils found near that place, partly in a bed of 

 calcareous blue clay, called Gait, which he considers as the 

 lowest bed of the Chalk formation, and which therefore should 

 seem to be the Chalk Marl of several modern writers ; whereas 

 Gait is more commonly applied to alluvial Clay, in the district 

 alluded to. I wish therefore to inquire of Mr. H. or any other 

 of your readers, whether some of the extraneous fossils there 

 mentioned, such as charred wood, mutilated Fish, Pentacrinites, 

 &c, were not found in moved and water-worn alluvial Clay, in- 

 stead of their being imbedded in stratified Chalk Marl P 

 I am, &;c. 



Teb. 2, 1815. A CONST a>;t Reader, 



XX. Letter from M. Ampere to Count Berthollet, on the 



Determination of the Proportions in which Bodies are corn- 

 lined, according to the respective Numler and Arrangement 

 of the Particles of ivhich their integrant Molecules are 

 composed. 



[Continued from p. 43'.] 



J.F we now proceed to consider the primitive forms of the cry- 

 stals recognised by mineralogists, and regard them as the re- 

 presentative forms of the most simple particles, admitting into 

 these particles as many molecules as the corresponding forms 

 have summits, we shall find that they are five in number ; the 

 tetrahedron, the octahedron, the parallelopipedon,the hexahedral 

 prism, and the rhomboidal dodecahedron. 



The particles corresponding to these representative forms are 

 composed of 4, 6, S, 12 and 14 molecules; the th»ee first of 

 tlicse numbers are those which we require to explain the forma- 

 tion of the gases to be immediately cited. I have shown in my 

 memoir that tlie number 12 is that which we must employ in 

 order to express the composition of the particles of several very 

 remarkable combinations, and that number 14 accounts for 

 that of the particles of the nitric acid, as it will be if we can 

 obtain it without water, for that of the particles of the muriate 

 of ammonia, &c. 



Let us now see how the molecules may be united according 

 to these different forms : 



Two molecules being supjjosed to be united on a line, to give 

 a clearer idea of their respective position j if we add thereto 



two 



