86 



CHEMISTRY. 



its body, which are affected, completely broken 

 up into clay, solid secondary or colloid silica, 

 and carbonate of potash. In the second case, 

 when a sufficient supply of carbonic acid can 

 not get within " chemical " distance of the feld- 

 spar molecules, clay is produced as before, only 

 more slowly, but the potash of the molecule is 

 carried off, a part as a carbonate and part as a 

 soluble silicate. Prom the plagioclase feldspar 

 the same conditions produce similar results, ex- 

 cept that the soluble silica which would be pro- 

 duced here is of course in combination with so- 

 dium. The author has found the soluble silica 

 of soils always in the form either of silicate of 

 potassium or of sodium, and very frequently 

 of both mixed. Biotite, by the continued action 

 of carbonic acid, oxygen, and 'water, loses mag- 

 nesia and iron, and becomes eventually the white 

 or yellow muscovite variety, which undergoes no 

 further chemical change. Hornblende, by car- 

 bonation, oxidation, and hydration, yields lime 

 as a carbonate until the whole of that base is 

 taken out. The pyrites of the rock is slow to 

 change, but it is also eventually acted on by wa- 

 ter and oxygen particularly, the latter combin- 

 ing with its substance here and there to form a 

 sulphate, which has a great mission in the physi- 

 ology of the soil. These chemical changes begin 

 on the exposed surfaces of the rock and along 

 the faces of the primary joints Then oxidation 

 begins in streaks and bands through the rock 

 mass, and around those areas carbonation is 

 most active. In fact, oxidation opens up the 

 rock for further change. The chemical changes 

 are followed by a new element in the making of 

 soil, in the action of organic matter, first living 

 as it finds footing in the already disintegrated 

 parts of the rock, and then dead. This in its 

 turn reacts to enforce the chemical changes, 

 bringing about reciprocal actions which make 

 the changes ever greater and more rapid ; or, as 

 the author summarizes the operation, " humus 

 is formed by lichens, and then higher plants; 

 following this, fungoid germs capable of assim- 

 ilating aerial nitrogen become abundant; finally, 

 all three processes mechanical, chemical, and 

 organic go merrily on together and contribute 

 all in their shares to the formation of an ever- 

 deepening soil, capable of supporting the life of 

 the highest plants. The humic acid, which is 

 formed by the inorganic decay of humus, has a 

 certain decomposing action, but it gradually 

 changes to carbonic acid, with the action of 

 which in this connection we have already dealt." 

 The power of micro-organisms to effect chem- 

 ical action was first studied by Pasteur in his 

 researches on fermentation. Our knowledge of 

 the work of bacteria in other industries has been 

 greatly advanced in the last few years, and 

 through the study of them some of the most im- 

 portant phenomena in agriculture have recently 

 received remarkable elucidation. One of the 

 most important plant foods in the soil is nitric 

 acid ; yet it occurs there already existent in only 

 the most minute proportions, being carried away 

 by rain or absorbed by vegetation as rapidly as 

 it is formed ; and it has been found that the soil, 

 under ordinary circumstances, continuously gen- 

 erates nitric acid from the various nitrogenous 

 manures that are applied to it. The researches 

 of Schloesing and Miintz have shown that the 



power of soils to convert the nitrogen of nitroge- 

 nous substances into nitric acid is due to mi- 

 cro-organisms or bacteria ; and these results have 

 been confirmed and greatly extended by other ex- 

 perimenters. Prof. Frankland proved in 1885 

 that some micro-organisms could grow in dis- 

 tilled water, or in the absence of organic matter. 

 By suitable cultures he separated the nitrifying 

 organisms from the others ; but it afterward ap- 

 peared that these organisms possessed the prop- 

 erty of converting ammonia into nitrous but 

 not into nitric acid. Further experiments showed 

 that the process of conversion into nitric acid 

 was a double one, and the work of two organ- 

 isms succeeding one another, and producing, the 

 first nitrous and the second nitric acid. The 

 second organism, or nitric ferment, resembles 

 potassium permanganate in its activity, in that 

 it has no effect on ammonia, but readily converts 

 nitrous into nitric acid. The fact of the multi- 

 plication of micro-organisms in distilled water, 

 and the further fact that the nitrification pro- 

 cess may be continued for four years in purely 

 mineral solutions, are strong presumptive evi- 

 dence in favor of their being able to gain a 

 livelihood in the entire absence of organic food 

 stuffs. This supposition is supported by the ex- 

 periments of M. Winogradsky, who has found that, 

 the nitrifying organisms flourish, multiply, and 

 actually build up living protoplasm in a solution 

 from which organic matter has been most thor- 

 oughly excluded. " Now," says Prof. Frankland, 

 " this living protoplasm in the experiments in 

 question must have been elaborated by these 

 bacteria from carbonic acid as the source of the 

 protoplasmic carbon, and from ammonia and 

 nitrous or nitric acids as the source of the proto- 

 plasmic nitrogen. If these experiments are cor- 

 rect . . . they are subversive of one of the funda- 

 mental principles of vegetable physiology, which 

 denies to all living structures, save those of 

 green plants alone, the power, of building up 

 protoplasm from such simple materials." The 

 question whether plants are capable of assimilat- 

 ing or utilizing as food the free nitrogen of the 

 atmosphere, which has been a very difficult one, 

 has been answered in the case of leguminous 

 plants by the researches of Prof. Hellriegel. Dr 

 Wilfarth, Dr. Gilbert, and Sir John Lawes. These 

 authors find that plants of this class are inhab- 

 ited by microbes whose presence is shown by 

 peculiar swellings or tuberosities on their roots, 

 through the agency of which a fixation of free 

 atmospheric nitrogen is accomplished. The re- 

 searches of Prof. Frankland, from whose paper 

 before the Royal Institution these facts are de- 

 rived, have further led to interesting results con- 

 cerning the selective action of micro-organisms., 

 their relations to the optical properties of certain 

 substances, and their individuality; and, as a 

 whole, they lead the author to the conclusions 

 that there may be around us numerous forms of 

 micro-organisms of the potentiality of which we 

 are still ignorant : and he has high anticipations 

 of the metamorphoses which it may be possible 

 to bring about through their agency. 



It had been shown by H. T. Brown and G. H. 

 Morris that during germination of grass seeds 

 the cell membrane of the endosperm is broken 

 down and destroyed by a specific cellulose-dis- 

 solving enzyme, or cytohydrolyst, such disin- 



