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NATURE 



{_Sept. 8, 1887 



between living and dead matter is not of a chemical nature. In 

 referring to chemical synthesis I cannot refrain from expressing 

 regret that so little has hitherto been done in the artificial pro- 

 duction of minerals with a view to elucidating the processes by 

 which they were formed in Nature, but it is possible that more 

 has been done in this direction than I am aware of, since this 

 is a department of chemistry with which I am not familiar. It 

 is certain that inorganic chemistry generally does not now 

 receive the attention which it formerly did. The exclusive 

 devotion to the chemistry of the carbon compounds which we 

 find in most of our laboratories at the present day may, however, 

 be accounted for when we see the brilliant results to which the 

 study of those compounds has led. 



After these few remarks on the development of chemistry 

 during the last fifty years, of which I know a little, it may seem 

 presumptuous on my part in the presence of some of the most 

 eminent chemists of our day, whose opinions must be of infinitely 

 more value than mine, to say anything about the future of our 

 science and the direction it will probably take. Nevertheless, 

 trusting to your kind indulgence, I will venture on some specu- 

 lations in this direction, which, if they do not instruct the younger 

 members of the Section, may serve to amuse their seniors, and 

 at all events will refer to subjects on which some thought is well 

 bestowed. 



As regards the future of chemistry, the question has fre- 

 quently suggested itself to me as it has doubtless done to others 

 — Will chemical science go on expanding and developing during 

 the next few generations as it has done in the course of the last 

 hundred years ? Will discovery follow discovery, and fact be 

 added to fact, until the record occupies not a few volumes only, 

 but a whole library ? Will systematic chemistry, i.e. the history 

 and description of all possible combinations of the elements, 

 have any limits? I am inclined to answer in the negative. All 

 human institutions pass through the same phases ; they have 

 their rise, they culminate, and decay ; and I do not see why the 

 science of chemistry should form an exception. Moreover, it is 

 a natural law that whatever develops rapidly also declines 

 rapidly, and the development of systematic chemistry since the 

 commencement of this century has been perfectly unprecedented. 

 I think it probable that in the course of time, at the rate at 

 which we are now progressing, nearly all possible compounds 

 will have been prepared, all the most important chemical facts 

 will have been discovered, and pure chemistry will then be 

 practically exhausted, and will be in the same condition as 

 systematic botany and mineralogy now are. New compounds 

 will now and then be discovered, just as new plants and new 

 minerals now are, but nothing further will be brought to light 

 that will affect the theories at which we shall then have arrived, 

 whatever they may be. All the material with which the science 

 has to deal having then been brought together, what will happen ? 

 Will chemical science cease? Will chemists, satisfied with past 

 achievements, cease to work, confining themselves to practical 

 questions and the history of the days gone by ? I think not. 

 'i'he science will continue to develop, but in other directions 

 than those previously pursued. The exhaustion of systematic 

 botany has not put an end to botanical science, for vegetable 

 physiology has opened a wide field to the botanist, one that will 

 take a long time to explore thoroughly. To indicate the direc- 

 tions which chemical science will take in its various applications 

 to other departments of knowledge, as, for instance, in con- 

 nexion with the study of the physical properties of matter, or in 

 elucidation of the chemical processes whereby minerals have 

 been formed, or those through which geological strata have 

 passed in bygone ages, would not be within my competency, as 

 J should have to touch on subjects with which I am not familiar ; 

 but I may be permitted to refer by a few words to a subject, 

 with which, by reading at least, I have become better acquainted, 

 and which seems to me to offer a wide field to the investigator 

 who shall come well provided with physical and chemical know- 

 ledge to its cultivation. I allude to the processes whereby the 

 substances constituting the various organs of plants and their 

 contents are formed, and those again to which the decomposition 

 and decay of vegetable matter are due; a subject as to which 

 our knowledge is quite elementary, but which, it seems to me, 

 admits of an extension and development of which we have at 

 present not the least conception. 



De Saussure, it is well known, first discovered the fact that 

 plants under the influence of light absorb carbonic acfd ^nd give 

 off oxygen, the inference of course being that the carbotiic acid 

 and the water present are decomposed, the carbon of the former 



.and the hydrogen of the latter going to form the various organic 

 constituents of the plant, while the oxygen or a part of it is set 

 at liberty and poured into the atmosphere. The facts as they 

 stand are simply these : what the plant requires for its subsist- 

 ence is carbonic acid, water, nitrogen in some form (presumably 

 that of a nitrate), certain bases — potash, lime, magnesia, iron 

 oxide, and phosphoric acid. Out of these it constructs the 

 whole of its organic frame, its cells and their contents, re- 

 arranging the elements of which its food consists in such a 

 manner as to convert inorganic into organic matter, i.e. changing 

 bodies in which the affinities of the atoms are thoroughly satis- 

 fied into such as contain them in a state of more or less unstable 

 equilibrium, and therefore liable to alteration when their atoms 

 are allowed to act in accordance with their natural affinities. 

 More than this we do not know ; our ignorance of the several 

 steps or stages of the process, if there are any such steps, is 

 complete ; all that has been added to the general statement just 

 given is mere speculation. Yet it is impossible to remain satis- 

 fied with the present state of our knowledge on the subject. 

 Accordingly numerous attempts have been made to bridge over 

 the chasm which separates the inorganic and organic worlds, not 

 indeed to show that the change does not involve the creation, as 

 was once supposed, of new matter — for this was proved long ago 

 — but to exhibit in its details the hidden mechanism which pro- 

 duces it, but hitherto without success. We know that light is 

 essential to the process of assimilation in plants, since this does 

 not proceed in the dark, but this fact does not help us to an 

 explanation, for light in this case is a mere stimulant, and never 

 produces the same or similar effects outside the vegetable 

 organism. Liebig and others have attempted to show that the 

 process of assimilation in plants commences with the formation 

 of some simply constituted body, such as oxalic or formic acid, 

 with the elimination of oxygen, out of which by condensation 

 and further separation of oxygen more complex bodies, such as 

 sugar, fats, &c., are formed ; but there is not the slightest 

 evidence at present in favour of this view. The first product of 

 assimilation that is distinctly recognized is starch, a highly com- 

 plex organic, we might almost say an organized body, which 

 appears at once with all its characteristic properties, like 

 Minerva springing fully armed from the head of Jove. If we 

 are to adhere to the facts so far observed, we must conclude that 

 the plant does not proceed as we should do in the laboratory, 

 beginning with the more simply constituted compounds and 

 advancing to the more complicated, but that the reverse process 

 is the one actually adopted, the supposed intermediate products 

 being more probably the results of retrogressive metamorphosis. 

 This conclusion is, however, so much opposed to ordinary 

 chemical views that one cannot feel surprised at the constantly 

 repeated attempts to clear up the question. There can be no 

 doubt indeed that much here remains to be done and to be 

 discovered. 



Intimately connected with this subject is that of chlorophyll, 

 the green-colouring matter of leaves, which is always found 

 wherever the process of assimilation in plants is going on, and 

 nowhere else, and is therefore doubtless an essential factor in 

 the process. What part it plays in this process is, in my 

 opinion, still unknown. Its action is probably in part chemical, 

 in part physical, and this adds, it may be, to the difficulty of 

 understanding it. It is generally supposed that it is chlorophyll 

 which by its direct action on the carbonic acid and water with 

 which it comes into contact leads to the formation of organic 

 matter with elimination of oxygen. But this is, I think, a mere 

 assumption — an error due, like many others, to a mistaken use 

 of terms. The chlorophyll of chemists is simply an organic 

 colouring matter, like alizarin or indigo, but being in the 

 vegetable cell intimately associated with other matters, vegetable 

 physiologists have attributed to the action of one, and that the 

 most obvious, constituent what is really due to the complex, 

 perhaps even to some quite other constituent of the complex. It 

 is impossible to conceive that the chlorophyll of chemists can be 

 endowed with the remarkable and exceptional properties attri- 

 buted to it by physiologists ; it is a chemical entity, nothing more. 

 It may indeed be said that chlorophyll only acts as it is stated to 

 do when inclosed =^within the vegetable cell, but this merely 

 amounts to saying that its action is not merely chemical, but is 

 controlled by the vitality of the cell, which, I suppose, means the 

 action of the protoplasm. If chlorophyll is the agent whereby 

 the decomposition of carbonic acid and wafer is effected, how, it 

 may be asked, is the agent itself produced ? It does not come 

 from without ; the plant must be able to form it in the first 



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