TRANSACTIONS OF SECTION B. 679 



4. On the Manufacture of Soda and Chlorine. By W. Weldon, F.B.S. 



5. On the Chemistry of the Natural Silicates. 

 By Professor T. Sterry Hunt, LL.D., F.B.S. 



The genesis of the crystalline stratified rocks, including the fundamental 

 granite and the succeeding crystalline eozoic schists, is a subject for the chemist, 

 without whose aid the natural history student, whether he styles himself 

 mineralogist or geologist, can never hope to solve this great riddle of geogeny. 

 The intervention of water, as taught by "Werner, in the formation of the granitic 

 substratum is now conceded, and we are prepared for a restatement of Neptunism 

 upon an igneous basis, as I have elsewhere attempted under the name of the 

 crenitic hypothesis. The chief chemical problem involved therein w T ill be evident 

 when we consider the composition of the rocks already referred to. These, 

 excluding carbonates, quartz, and non-silicated oxides, are made up essentially of 

 silicates, hydrous or anhydrous of a few bases, chiefly potash, soda, lime, magnesia, 

 ferrous oxide, and alumina. The most important distinction among these is that 

 between aluminous and non-aluminous silicates, due to the ready solubility and 

 wide diffusion of salts of the protoxide bases in natural waters, and to the stability 

 and insolubility of the silicates of alumina. Of natural aluminous silicates we 

 have a series from simple hydrous and anhydrous species, through the pinites and 

 muscovites and damourites, in which the oxygen ratio of protoxide to alumina is 

 1 : 12, 1:9, or 1 : 6. "We then come to the great zeolite and feldspar group in 

 which it is 1:3, and to silicates like epidote, garnet, magnesian micas and 

 chlorites, in which it becomes 1 : 1 and even 2:1. That of the feldspar, which 

 we may call the normal ratio, is found also in aluminates, and its significance is 

 clear to the chemist. Aluminous double silicates with this ratio are formed in 

 solutions in presence of excess of alkalies, and appear as natural results of aqueous 

 action on igneous basic rocks as seen in basalts, in amygdaloids, and in volcanic 

 mud in the deep sea. The studies of Bunsen and those of Dauhree throw great 

 light on this process. The simultaneous production in many cases of protoxide 

 silicates like pectolite, gyrolite, okerite, and apophyllite, is nex'; to be considered. 

 All of these are non-magnesian, but by reaction on dissolved salts of magnesia take 

 up this base by exchange. Hence serpentines, chrysolite, pyroxene and talc. 



The decomposition by heat of alkaline solutions of alumina and silica, in some 

 cases with depositions of quartz and productions of more basic solutions which 

 react with magnesian salts, explains the origin of aluminous silicates with excess 

 of protoxide bases. The power of alkaline silicates in aqueous solution to hold 

 dissolved various metallic oxides, throws light in the production of oxides of the 

 spinel and corundum groups. 



The origin of simple aluminous silicates and others with small amounts of 

 protoxide is found in the diagenesis of the kaolin from subaerial decay of feldspathic 

 rocks, soluble silicates of the zeolitic type often intervening. 



In the various reactions set forth in this paper it was said that we have, by the 

 working of known chemical laws, an explanation of the genesis of the great- 

 groups of natural silicates and the basis of a rational system of mineralogy and of 

 lithology. 



6. On the Liquefaction of Oxygen and the Density of Liquid Hydrogen. 

 By Professor James Dewar, M.A., F.B.S. 



7. On the Physical Constants of Solutions. By Professor "W. L. Goodwin, 

 D.Sc, and Professor D. H. Marshall, M.A., F.B.S.E. 



Previous experimenters have prepared solutions containing m molecules of 

 anhydrous chlorides to n molecules of water. Such solutions do not contain 

 equal numbers of molecules of the salts in equal volumes of the solutions. The 



