DECEMBER 18, 1913} 
purposes. Among the exhibits of Messrs. Isenthal 
and Co. was a collection of pladuram products, a 
form of tungsten specially treated, which it is hoped 
to apply to purposes where a hard, inert metal is 
required. Radio-active preparations were shown by 
Mr. F. Harrison Glew. The principal exhibit of 
Messrs. Muirhead and Co. was a Heurtley magnifier 
for use in cable telegraphy or wireless telegraphy, or 
wherever it is required to magnify the effect of small 
mechanical movements. Instruments connected with 
wireless telegraphy were shown by the Marconi Com- 
pany, the Ludgate Wireless Company, and Messrs. 
Graham and Latham, while very complete exhibits 
of projection apparatus and microscopes for all pur- 
poses were shown by Messrs. Carl Zeiss, Messrs. E. 
Leitz, Messrs. Newton and Co., and other firms. 
The instruments of Messrs. H. Tinsley and Co. for 
cclour measurement and for lens testing, and the 
new miniature precision instruments of the Weston 
Co., are also worthy of mention. 
THIRD INTERNATIONAL CONGRESS OF 
TROPICAL AGRICULTURE. 
HE first International Congress of Tropical Agri- 
culture was held in Paris in 1905, and was 
organised by a number of French men of science 
interested in this subject. At its close the Association 
Scientifique Internationale d’Agronomie Coloniale et 
Tropicale was founded, to promote in every possible 
way scientific work in tropical agriculture. Branches 
of this association were gradually founded in Bel- 
gium, France, Germany, Great Britain, Italy, Portu- 
gal, and elsewhere, until at present practically every 
country interested, either on its own account or 
through its colonies, in tropical agriculture, is repre- 
sented on the Central Bureau of the association, 
which has its headquarters in Paris. In 1910 a very 
successful second Congress of Tropical Agriculture 
was held in Brussels. At the close of that congress 
M. de Lanessan, formerly Governor-General of Indo- 
China, who had up till that time been president of 
the association, retired, and was succeeded by Prof. 
Wyndham Dunstan, C.M.G., F.R.S., director of the 
Imperial Institute. 
The International Association has decided to hold 
the third Congress of Tropical Agriculture in London, 
at the Imperial Institute, on June 23-30 next year, 
under the presidency of Prof. Dunstan. A strong 
organising committee, including Sir D. Prain, direc- 
tor of the Royal Gardens, Kew; Sir S. Stockman, 
chief veterinary officer to the Board of Agriculture 
and Fisheries; Mr. Bernard Coventry, Agricultural 
Adviser to the Government of India; Dr. F. Watts, 
Imperial Commissioner of Agriculture for the West 
Indies, and other eminent authorities on tropical agri- 
culture, has been at work for some time in prepara- 
tion for the congress. 
It is proposed to devote the afternoon meetings of 
the congress to papers, and the morning meetings to 
a series of discussions on important problems of 
special interest, such as technical education and re- 
search in tropical agriculture; outstanding scientific 
problems in rubber production; methods of develop- 
ing cotton cultivation in new countries; problems of 
fibre production; agriculture in arid regions; and 
hygiene and preventive medicine, in their relation to 
tropical agriculture. The organising committee will 
welcome contributions on these or allied subjects. 
For further information regarding the arrangements 
for the congress, the communication of papers, &c., 
application should be made to the organising secre- 
taries (Dr. T. A. Henry and Mr. H. Brown), Third 
International Congress of Tropical Agriculture, Im- 
perial Institute, London, S.W 
NO. 2303, VOL. 92] 
NATURE 
461 
PHYSICAL CHEMISTRY OF SOLUTIONS. 
Ae is well known, the progress in the physical 
chemistry of solutions which has been made 
during the last thirty years, though extensive and 
detailed in a certain sense, has nevertheless suffered 
not a little from the fact that fully 90 per cent. of 
the investigations have been restricted to the study of 
the behaviour of substances dissolved in water. At 
the present time, therefore, whilst a very large amount 
of data has been accumulated upon the subject of 
aqueous solutions, our knowledge of the behaviour of 
non-aqueous solutions and solutions formed in mixed 
solvents is deplorably scanty. Of course, here and 
there the subject has been attacked, especially within 
the last decade, and a few general conclusions have 
been laboriously attained. Many of the rules, how- 
ever, which serve as a trustworthy guide in the case 
of aqueous solutions have to be considerably modified 
or even discarded altogether when we come to non- 
aqueous solutions. At the same time, it is clear that 
the problem of solution in general cannot be regarded 
as in a satisfactory state, so long as generalisations 
applicable to a large number of solvents at least are 
wanting. 
It is for this reason that we welcome the mono- 
graph published by Prof. H. C. Jones, entitled ‘‘ The 
freezing point-lowering, conductivity, and viscosity of 
solutions of certain electrolytes in water, methyl 
alcohol, ethyl alcohol, acetone, and glycerol, and in 
mixtures of these solvents with one another ’’ (Pub- 
lication No. 180, Carnegie Institution of Washington). 
The present work is to be regarded as supplementary 
to Publication No. 80 of the same institution. The 
actual experimental work has been carried out by 
several investigators, under the direction of Prof. 
Jones. Each of these investigators, after giving an 
account of the experimental methods and results ob- 
tained for various salts—inorganic salts—in various 
solvents, pure and mixed, makes a very brief sum- 
mary of conclusions, the whole field being finally 
reviewed by Prof. Jones himself in a general dis- 
cussion, which occupies the last dozen pages or so of 
the book. As was to be expected, great stress is laid 
upon the generality of the phenomenon of solvation 
and much of the work is devoted to the elucidation— 
naturally with varying success—of the three funda- 
mental factors:—(1) Change in solvation, which 
changes the mass and size of the ion; (2) change in 
the viscosity of the solution with change in tempera- 
ture thereby affecting the friction of the ions in 
moving through the solution; and (3) change in the 
number of dissolved particles—molecules and ions. 
The publication as a whole is a monument of in- | 
dustry which reflects the greatest credit upon the 
laboratory from which it emanates. It is sincerely to 
be hoped that the systematic accumulation of similar 
data will become much more general than has hitherto 
been the case. 
PHYSIOLOGY AT THE BRITISH 
ASSOCIATION. 
THs has been a year of congresses for physio- 
logists. The International Congress of Medi- 
cine, the International Congress of Physiology, and 
the British Association all took place during August 
and September. In spite of the fact that the British 
. Association came last, the section of physiology had 
a very successful meeting. 
The president’s address was especially interesting, 
as it gave the views of an organic chemist on the 
physico-chemical aspect of his work. The address 
has already appeared in Narure (October 16, p. 213). 
