January 28, 1904] 
NATURE 
307 
plants is called for. Much has been learned since Liebig 
founded the science of agricultural chemistry. It was he 
who pointed out some of the ways by which it is possible 
to increase the fertility of a soil. Since the results of his 
investigations were given to the world the use of artificial 
fertilisers has become more and more general. 
But it is one thing to know that artificial fertilisers are 
useful and it is quite another thing to get them. At first 
bone dust and guano were chiefly used. Then as these 
became dearer, phosphates and potassium salts from the 
mineral kingdom came into use. 
At the Fifth International Congress for Applied Chem- 
istry, held at Berlin, Germany, last June, Dr. Adolph Frank, 
of Charlottenburg, gave an extremely interesting address 
on the subject of the use of the nitrogen of the atmosphere | 
| far obtained. 
for agriculture and the industries, which bears upon the 
problem that we are dealing with. Plants must have 
nitrogen. At present this is obtained from the great beds 
of saltpetre found on the west coast of South America— 
the so-called Chili saltpetre—and also from the ammonia 
obtained as a by-product in the distillation of coal, especially 
in the manufacture of coke. The use of Chili saltpetre for 
agricultural purposes began about 1860. In 1900 the 
quantity exported was 1,453,000 tons, and its value was 
about 60,000,000 dollars. In the same year the world’s 
production of ammonium sulphate was about 500,000 tons, 
of a value of somewhat more than 20,000,000 dollars. Of 
these enormous quantities about three-quarters find appli- 
cation in agriculture. The use of these substances, 
especially of saltpetre, is increasing rapidly. At present 
it seems that the successful cultivation of the soil is depen- 
dent upon the use of nitrates, and the supply of nitrates is 
limited. Unless something is done we may look forward 
to the time when the earth, for lack of proper fertilisers, 
will not be able to produce as much as it now does, and 
meanwhile the demand for food is increasing. According 
to the most trustworthy estimations indeed, the saltpetre 
beds will be exhausted in thirty or forty years. Is there a 
way out? Dr. Frank shows that there is. In the air there 
is nitrogen enough for all. The plants can make only a 
limited use of this directly. For the most part it must be 
in some form of chemical combination, as, for example, a 
nitrate or ammonia. The conversion of atmospheric 
nitrogen into nitric acid would solve the problem, and this 
is now carried out. But Dr. Frank shows that there is 
another, perhaps more economical, way of getting the 
nitrogen into a form suitable for plant food. Calcium 
carbide can now be made without difficulty, and is made 
in enormous quantities by the action of a powerful electric 
current upon a mixture of coal and lime. This substance 
has the power of absorbing nitrogen from the air, and the 
product thus formed appears to be capable of giving up its 
nitrogen to plants, or, in other words, to be a good fertiliser. 
It is true that this subject requires further investigation, 
but the results thus far obtained are full of promise. If the 
outcome should be what we have reason to hope, we may 
regard the approaching exhaustion of the saltpetre beds 
with equanimity. But, even without this to pin our faith 
to, we have the preparation of nitric acid from the nitrogen 
and oxygen of the air to fall back upon. 
While speaking of the food problem, a few words in re- 
gard to the artificial preparation of foodstuffs. I am sorry 
to say that there is not much of promise to report upon in 
this connection. In spite of the brilliant achievements of 
chemists in the field of synthesis it remains true that thus 
far they have not been able to make, except in very small 
quantities, substances that are useful as foods, and there is 
absolutely no prospect of this result being reached within 
a reasonable time. A few years ago Berthelot told us of 
a dream he had had. This has to do with the results that, 
according to Berthelot, are to be brought about by the 
advance of chemistry. The results of investigations already 
accomplished indicate that, in the future, methods will 
perhaps be devised for the artificial preparation of food from 
the water and carbonic acid so abundantly supplied by 
nature. Agriculture will then become unnecessary, and the 
landscape will not be disfigured by crops growing in geo- 
metrical figures. Water will be obtained from holes three 
or four miles deep in the earth, and this water will be 
NO. 1787, VOL. 69] 
above the boiling temperature, so that it can be used as a 
source of energy. It will be obtained in liquid form after 
it has undergone a process of natural distillation, which 
will free it from all impurities, including, of course, disease 
germs. The foods prepared by artificial methods will also 
be free from microbes, and there will consequently be less 
disease than at present. Further, the necessity for killing 
animals for food will no longer exist, and mankind will 
become gentler and more amenable to higher influences. 
There is, no doubt, much that is fascinating in this line of 
thought, but whether it is worth following depends upon 
the fundamental assumption. Is it at all probable that 
chemists will ever be able to devise methods for the artificial 
preparation of foodstuffs? 1 can only say that to me it 
does not appear probable in the light of the results thus 
I do not mean to question the probability of 
the ultimate synthesis of some of those substances that are 
of value as foods. This has already been accomplished on 
the small scale, but for the most part the synthetical pro- 
cesses employed have involved the use of substances which 
themselves are the products of natural processes. Thus, the 
fats can be made, but the substances from which they are 
made are generally obtained from nature and are not them- 
selves synthetical products. Emil Fischer has, to be sure, 
made very small quantities of sugars of different kinds, but 
the task of building up a sugar from the raw material 
furnished by nature—that is to say, from carbonic acid and 
water—presents such difficulties that it may be said to be 
practically impossible. 
When it comes to starch, and the proteids which are the 
other chief constituents of foodstuffs, the difficulties are still 
greater. There is not a suggestion of the possibility of 
making starch artificially, and the same is true of the pro- 
teids. In this connection it is, however, interesting to note 
that Emil Fischer, after his remarkable successes in the 
sugar group and the uric acid group, is now advancing upon 
the proteids. I have heard it said that at the beginning of 
his career he made out a programme for his life work. This 
included the solution of three great problems. These are 
the determination of the constitution of uric acid, of the 
sugars and of the proteids. Two of these problems have 
been solved. May he be equally successful with the third! 
Even if he should be able to make a proteid, and show 
what it is, the problem of the artificial preparation of food- 
stuffs will not be solved. Indeed, it will hardly be affected. 
Although science is not likely, within periods that we 
may venture to think of, to do away with the necessity of 
cultivating the soil, it is likely to teach us how to get more 
out of the soil than we now do, and thus put us in a posi- 
tion to provide for the generations that are to follow us. 
And this carries with it the thought that, unless scientific 
investigation is kept up, these coming generations will be 
unprovided for. 
Another way by which the food supply of the world can 
be increased is by relieving tracts of land that are now used 
for other purposes than the cultivation of foodstuffs. The 
most interesting example of this kind is that presented by 
the cultivation of indigo. There is a large demand for this 
substance, which is plainly founded upon zsthetic desires 
of a somewhat rudimentary kind. Whatever the cause may 
be, the demand exists, and immense tracts of land have been 
and are still devoted to the cultivation of the indigo plant. 
Within the past few years scientific investigation has shown 
that indigo can be made in the factory from substances 
the production of which does not for the most part involve 
the cultivation of the soil. In 1900, according to the report 
of Dr. Brunck, managing director of the Badische Anilin- 
und Soda-Fabrik, the quantity of indigo produced annually 
in the factory ‘‘ would require the cultivation of an area 
of more than a quarter of a million acres of land (390 square 
miles) in the home of the indigo plant.’’ Dr. Brunck 
adds :—‘‘ The first impression which this fact may be likely 
to produce is that the manufacture of indigo will cause a 
terrible calamity to arise in that country; but, perhaps not. 
If one recalls to mind that India is periodically afflicted with 
famine, one ought not, without further consideration, to 
cast aside the hope that it might be good fortune for that 
country if the immense areas now devoted to a crop which 
is subject to many vicissitudes and to violent market changes 
