Decembkr 1, 1898.] 



KNOWLEDGE. 



237 



These diagrams deal with weather in the past ; do they 

 afford any clue to the future '? 



18-KJ '1. 'S '52 'fi '00 '4 S' '72 'li 'MO '4 '8 '92 



30 



2S 



26 - 



24 



22 



20 



Fig. 3. 



In the case of the Eothesay curve and others like it, 

 whatever view we may take of the correspondence with 

 the sunspot curve, the fact of that correspondence having 

 subsisted so many years seems to afibrd some basis for 

 expecting it to continue ; in which case the curves would 

 now be nearing another maximum. On the other hand, 

 there is the thirty-five years' period in the east of England 

 (a period which, by the way, is just about three times that 

 of the solar cycle). Should this cycle of Brueckner's 

 continue to be realized, we might expect those smoothed 

 curves to attain their next conspicuous maximum some- 

 where about 1912. With regard to the other curves there 

 is not much to be said. They appear to have all lately 

 passed a low minimum, and the rise seems likely to con- 

 tinue. The present crest-interval (reckoning from the 

 last prominent crest) promises to be longer than eleven 

 years. The recent years, 1887, 1888, 1889, 1890, and 

 1892, have all (according to Symons) shown a deficiency 

 of rainfall in England, and we may reasonably infer that 

 the years now approaching will be wetter, though the 

 wetness might not appear in the summer half of the 

 year, when it would be most noticed. But in all such 

 endeavours to penetrate the future, it is wholesome to bear 

 in mind the plentiful stultification to which over-confident 

 weather prophets have had to submit hitherto. 



NITROGEN AS FOOD FOR ANIMALS AND 

 PLANTS. 



By Vaughan Cor.nisii, M.Sc, F.C.S. 



T 



I HE atmospheric fluid, or common air," Lavoisier 

 wrote, "is composed of two gases or auriform 

 fluids, one of which is capable, by re.spiration, 

 of supporting animal life, and in it metals arc 

 calcinable and combustible bodies may bum ; 

 the other, on the contrary, is endowed with directly 

 opposite qualities — it cannot be breathed by animals, 

 neither will it admit of the combustion of inflammable 

 bodies, nor of the calcination of metals. 



" We have given to the base of the former, which is the 

 respirable portion of atmospheric air, the name of oxygen. 

 . . . The chemical properties of the noxious portion of 

 atmospheric air being hitherto but little known, we have 

 been satisfied to derive the name of its base from its 

 known qualities of killing such animals as are forced to 

 breathe it, giving it the name of azot, from the Greek 

 privitive particle a and fwi;, vita : hence the name of the 

 noxious part of atmospheric air is azotic gas." 



Lavoisier, who was the first clearly to state the chemical 

 nature of air as composed of two substances, one chemically 

 active and the other chemically inert, occupied himself for 

 many years in developing the knowledge of the chemistry 

 of oxygen — the active constituent of air. The readiness 

 with which oxygen gas can be made to act upon and com- 

 bine with other substances enables its chemical functions 

 to be determined with comparative ease, and the mode in 

 which this element is used in the nourishment of the animal 

 body was soon elucidated with tolerable completeness ; on 

 the other hand, the inertness of a:ot (or nitrogen, as the 

 substance soon came to be called in England) rendei*ed the 

 chemical study of this constituent of the atmosphere a less 

 attractive as well as a slower and more laborious pursuit. 

 Thus, if we compare the ways in which the oxygen and 

 nitrogen of the air are taken hold of to build up the animal 

 body, we find that one process is direct and in its main 

 features simple, whereas the processes by which the 

 nitrogen of the air becomes a constituent of the flesh and 

 muscleare, on the contrary, indirect and complicated. Even 

 at the present time, a huudi-ed years after the researches of 

 Lavoisier, the mode of " assimilation of nitrogen " is only 

 beginning to be understood. When air enters the hollow 

 cells of the lungs, the blood, flowing round the cells in 

 little veins and capillaries, seizes upon and " fixes " the 

 oxygen, which freely passes through the thin walls of the 

 air-cells, and carries to every part of the body the combined 

 oxygen which it has thus seized upon. Parting in its 

 passage through the body with the oxygen which it has 

 seized from the air, the blood acts as carrier of oxygen 

 from the air to the muscle, flesh, nerve, and other parts of 

 the body. But the blood has no power to seize upon and 

 fix the nitrogen gas which enters the lungs at every breath. 

 The blood has to obtain its nitrogen from the animal and 

 plant food which is taken into the stomach ; the throat 

 and not the windpipe is the channel by which the nitrogen 

 of the air is supplied to the body. Animals used by man 

 for food obtain their nitrogen from plants. Plants have 

 to depend ultimately upon the an- for their supply of 

 nitrogen. 



The plant, however, does not appear to be able 

 assimilate the free atmospheric nitrogen through 

 leaves any more than an animal can assimilate the 

 through its lungs. Leaves catch the carbonic acid of the 

 air as the lungs of animals catch the oxygen of the air ; 

 but the nitrogen, it seems, has to reach the sap through 



to 



its 



gas 



