474 



NATURE 



\Scpt. 1 6, i8So 



tion" was established at Mocheni, near Leipzig, in 1S51-52. In 

 1S77 the twenty-fiftli anniversary of the foundation of that insti- 

 tution nas celebrated at Leipzig, when an account (which has 

 since been published) was given of the number of stations then 

 existing, of the number of chemists engaged, and of the subjects 

 which had been investigated. From that statistical statement 

 we learn that in 1877 the number of stations was 122. 



Besides these stations on the Continent of Europe, the United 

 States are credited with one, and Scotland also with one. 



Each of these stations is under the direction of a chemist, 

 frequently with one or more assistants. One special duty of 

 most of them is what is called manure- or seed- or feeding-stuff- 

 control; that is, to examine or analyse, and report upon such 

 substances in the market, and it seems to have been found to the 

 interest of dealers in these commodities to submit their proceed- 

 ings to a certain degree of supervision by the chemist of the 

 station of their district. 



But agricultural research has always been a characteristic 

 feature of these institutions. It is stated that the investigation 

 of soils has been the prominent object at 16 of them, experi- 

 ments with manures at 24, vegetable physiology at 2S, animal 

 physiology and feeding experiments at 20, vine culture and wine 

 making at 13, forest culture at 9, and milk production at 11. 

 Others, according to their locality, have devoted special attention 

 to fruit culture, olive culture, the cultivation of moor, bog, and 

 peat land, the production of silk, the manufacture of spirit, and 

 other products. 



Nor does this enumerations of the institutions established as the 

 direct result of Liebig's influence, and of the subjects investigated 

 under their auspices, complete the list either of the workers 

 engaged, or of the work accomplished in agricultural research. 

 To say nothing of the labours of Boussingault, which commenced 

 some years prior to the appearance of Liebig's first work, and 

 which are fortunately still at the service of agriculture, important 

 contributions have been made by the late Professors Johnston 

 and Anderson in Scotland, and in this country both by Mr. 

 Way and Dr. Voelcker, each alike in his private capacity, and 

 in fulfilment of his duties as Chemist to the Royal Agricultural 

 Society of England. Nor would it be fair to Mr. Lawes (who 

 commenced experimenting first with plants in pots, and after- 

 wards in the field, soon after entering into possession of his 

 property in 1S34, and with whom I have myself been associated 

 since 1S43), were I to omit in this place any mention of the 

 investigations w hich have _been so many years in progress at 

 Rothamsted. 



So much for the machinery ; but what of the results achieved 

 by all this activity in the application of chemistry to agriculture ? 



The more I have looked at the subject with the hope of treating 

 it comprehensively, the more I have been impelled to substitute 

 a very limited plan for the much more extended scheme which I 

 had at first hoped to be able to fill up. I propose then to con- 

 fine attention to a few special points, which have either some 

 connection with one another, or to which recent results or 

 discussions lend some special interest. 



First as to the sources and the assimilation of the carbon, the 

 hydrogen, and the oxygen of vegetation. From the point of 

 view of the agricultural chemist, the hydrogen and the oxygen 

 may be left out of view. For, if the cultivator provide to the 

 plant the conditions for the accumulation of sufficient nitrogen 

 and carbon, he may leave it to take care of itself in the matter 

 of hydrogen and oxygen. That the hydrogen of the carbo- 

 hydrates is exclusively obtained from water, is, to say the least, 

 probable ; and whether part of their oxygen is derived from 

 carbonic acid, and part from water, or the whole from either of 

 these, will not affect his agricultural practice. 



With regard to the carbon, the wliole tendency of subsequent 

 observations is to confirm the opinion put forward by Dr. 

 Saussure about the commencement of the century, and so forcibly 

 insisted upon by Liebig forty years later — that the greater part, 

 if not the whole of it, is derived from the carbonic acid of the 

 atmosphere. Indeed, direct experiments are not w anting — those 

 of Moll, for example — from which it has been concluded that 

 plants do not even utilise the carbonic acid which they may take 

 up from the soil by their roots. However this may be, we may 

 safely conclude that practically the whole of the carbon ^^■hich 

 it is the object of the cultivator to force the plants he grows to 

 take up is derived from the atmosphere, in which it exists in 

 >uch extremely small proportion, but nevertheless large actual, 

 and constantly renewed amount. 



Judging from the more recent researches on the point, it would 



seem probable that the estimate of one part of carbon, as car- 

 bonic acid, in 10,000 of air, is more probably too high than too 

 low as an estimate of the aver.ige quantity in the atmosphere of 

 our globe. And, although this corresponds to several times 

 more in the column of air resting over an acre of land tlian the 

 vegetation of that area can annually take up, it represents an 

 extremely small amount at any one time in contact with the 

 growing plants, and could only suffice on the supposition of a 

 very rapid renewal accomplished as the result, on the one hand, 

 of a constant return of carbonic acid to the atmosphere by com- 

 bustion and the respiration of a.iimaU, and, on the other, of a 

 constant interchange and equalisation among the constituents of 

 the atmosphere. 



It will convey a more definite idea of what is accomplished by 

 vegetation in the assimilation of carbon from the atmosphere if I 

 give, in round numbers, the results of some direct experiments 

 made at Rothamsted, instead of making general statements 

 merely. 



In a field which has now grown wheat for thirty seven years 

 in succession there are some plots to uhich not an ounce of 

 carbon has been returned during the whole of that period. Yet, 

 with purely mineral manure, an average of about 1,000 pounds 

 of carbon is annually removed from the land ; and where a given 

 amount of nitrogenous manure is employed with tiie mineral 

 manure, an average of about 1,500 pounds per acre per annum 

 more is obtained ; in all an average of about 2,500 pounds of 

 carbon annually assimilated over an acre of land without any 

 return of carbonaceous manure to it. 



In a field in which barley has been grown for twenty-nine 

 years in succession, quite accordant results have been obtained. 

 There smaller amounts of nitrogenous manure have been em- 

 ployed with the mineral manure than in the experiments with 

 wheat above cited ; but the increase in the assimilation of carbon 

 for a given amount of nitrogen supplied in the manure is greater 

 in the case of the barley than of the wheat. 



With sugar-beet again, larger amounts of carbon have been 

 annually accumulated without the supply of any to the soil, but 

 under the influence of a liberal provision of both nitrogenous and 

 mineral manure, than by either wlieat or barley. 



I^astly, with grass, still larger amounts of carbon have beer» 

 annually accumulated, without any supply of it by manure. 



Many experiments have been made in Germany and elsewhere, 

 to determine the amount of the different constituents taken up 

 at different periods in the growth of various plants. But we 

 may refer to some made at Rothamsted long ago to illustrate 

 the rapidity with which the carbon of our crops may be 

 withdrawn from the atmosphere. 



In 1S47 we carefully took samples from a glowing wheat crop 

 at different stages of its progress, commencing on June 21, and 

 in these samples the dry matter, the mineral matter, the nitrogen, 

 &c., were determined. On each occasion the produce of two 

 separate eighths or sixteenths of an acre was cut and weighed, 

 so that the data were provided to calculate the amounts of the 

 several constituents which had been accumulated per acre at 

 each period. The result was that, whilst during little more thart 

 live weeks from June 21 there was comparatively little increase 

 in the amount of nitrogen accumulated over a given area, more 

 than half the total carbon of the crop was accumulated during 

 that period. 



I should say that determinations of carbon, made in samples 

 of soil taken from the wheat-field at different periods during 

 recent years, indicate some decline in the percentage of carbon 

 in the soils, but not such as to lead to the supposition that the 

 soils have contributed to the carbon of the crops. Besides the 

 amount of carbon annually removed, there w ill of course be a 

 further accumulation in the stubble and roots of the crops ; and 

 the reduction in the total carbon of the soil, if such have_ really 

 taken jjlace, would show that the annual oxidation within the 

 soil is greater than the annual gain by the residue~of the crops. 



Large as is the annual accumulation of carbon from the atmo- 

 sphere over a given area in the cases cited, it is obvious that the 

 quantity must vary exceedingly with variation of climatal condi- 

 tions. It is, in fact, several times as great in the case of tropical 

 vegetation — that of the sugar-cane, for example. And not only 

 is the 'gi-eater part of the assimilation accomplished within a 

 comparatively small portion of the year (varying of course 

 according to the region), but the action is limited to the hours of 

 daylight, whilst during darkness there is rather loss than gain. 



But it is remarkable that whilst the accumulation of carbon, 

 the chief gain of solid material, takes place under the influence 



