880 
NATURE 
. 
[JUNE 30, 1923 

An Einstein Paradox. 
THE letter with the above title in Nature of June 2, 
Pp. 742, contained two oversights which I should like 
to be allowed to correct. 
I. In the second part I inadvertently changed the 
meaning of x’, Overlooking the fact that x’ in the 
first part meant, by implication, the distance of K, 
from L at the time that the light reached him, I 
used it in the second part as the distance K,L at 
the instant the signal was given. I should have 
employed a different letter, ¥,; and then, if required, 
x’ =c/(c+v) of #3. 
-2. A term was omitted from the value of x’, 
which should have been (1 +v/c)% — vt. 
} R. W. GENESE. 
40 London Road, Southborough, 
June 13. 

The Concilium Bibliographicum. 
My attention has been directed to a statement in 
Nature of April 28, p. 584, made in connexion with 
the report of a meeting concerning the ‘‘ Zoological 
Record.”’ It is stated that ‘‘ With the exception of 
the ‘ Archiv fiir Naturgeschichte,’ which is about 
nine years behindhand and consequently of very 
little use, the ‘ Zoological Record’ is at present the 
only bibliographic guide to zoological literature being 
published in the whole world.” 
Permit me to recall that the Concilium Biblio- 
graphicum at Zurich, founded in 1895 by Dr. Herbert 
Haviland Field and approved by the International 
Zoological Congress, is still continuing his work. 
After Dr. Field’s death in 1921, the Concilium was 
placed under the auspices of the Swiss Society of 
Natural Sciences and the United States National 
Research Council, and has published since that time 
volumes 30 and 31 of the “‘ Bibliographia Zoologica,” 
containing an international review of zoological 
papers. Two other volumes (32 and 33) are already 
in progress of publication. J. STROHL, 
Director of the Concilium 
Bibliographicum., 
49 Hofstrasse, Zurich, 
May 15. 

[We have also received a letter from Messrs. Louis 
B. Prout and George Talbot, of the Hill Museum, 
Witley. They suggest the issue of cards so that 
“subscribers would have the current literature 
available say every month, and no one would be 
obliged to purchase sections which would not be 
useful to him.’’ They too direct attention to the 
reorganisation of the Concilium Bibliographicum and 
strongly urge co-operation with it. 
Zoologists will be glad to learn that the Concilium 
Bibliographicum is still in being. There was some 
excuse for the incorrect statement to which Dr. 
Strohl objects, for inquiry at the two chief zoological 
libraries in London has failed to produce a volume 
of “‘ Bibliographia Zoologica’’ later than vol. xxx., 
which, though it purports to deal with the literature 
down to the end of 1920, is mainly composed of titles 
from 1915-1917 ; it also omits Lepidoptera, Hymeno- | 
ptera, and Vertebrata. But, even were ‘“ Biblio- 
graphia Zoologica ’’ more up-to-date, more complete, 
and more accessible, its plan scarcely enables it to 
compete with the “ Zoological Record”’ for the 
support of systematists. In the past the peculiar 
contribution of the Concilium has been the separate 
cards, but we have not seen any of these for a long 
time. We hope their issue has not ceased, for it is 
along those lines that co-operation seems most 
NO. 2800, VOL. 111] 
| of the past has been little more than instruction. 

promising. If the Concilium could furnish the titles 
completely and promptly, the Zoological Recorders 
could work up the analytical index they have been 
accustomed to provide. We may remind Messrs. 
Prout and Talbot that the several sections of the 
“ Zoological Record ’’ have been sold separately for 
the past twenty years.—Ep. NaTurE.] ad 

Educational Problems of Tropical Agriculture. 
It is exceedingly important at the present moment 
that the attention of men of science should be directed 
to some of the needs and problems connected with 
tropical agricultural education. As many readers of 
NATURE are aware, a college of tropical agriculture, 
the only one of its kind with pretensions to University 
standing within the Empire, was opened last year in 
Trinidad, and the ultimate success of this institution, 
both from the point of view of education and research, 
will, quite irrespective of financial support, depend 
upon the institution’s outlook and policy and, what 
is equally important, the degree of acceptance which 
this receives in Great Britain and America. 
In England agricultural colleges have not, from 
an academic point of view, achieved a very high 
status; nor have they been free from adverse 
criticism on the part of practical farmers. The 
policy of the institutions, therefore, has been some- 
what unstable, tending to oscillate between the solar 
force of the universities and the lunar attraction of 
the practical farmers. This condition has been 
produced through misunderstandings on the following 
points: (a) the nature of agriculture ; (b) the defini- 
tion of the word “ practical ’’; and (c) the difference 
between education and instruction. 
Agriculture is to some extent an art and to some 
extent a profession, but fundamentally and com- 
prehensively it is a business, or, if another term be 
preferred, it is biological industry. The trouble has 
been that most students of agriculture have thought 
of it as a profession, whereas the practical farmers 
have regarded it as an art. By definition, both are 
wrong fundamentally. Unenlightened, the students 
have tended to specialise in applied natural science 
(often of questionable quality), while the farmers 
have been the advocates of concentration on the art 
(‘‘ real practical work ’’). The misunderstanding as to 
the word “ practical” is, therefore, clear. Neither is 
practical; for agriculture is fundamentally econ- ~ 
omics, in which faculty practical work can be purely 
intellectual, for example, accountancy and statistical 
inquiry. Misconceptions as to the meaning of 
practical have been responsible for confusion as to 
the difference between education and instruction. 
The word instruction should be relegated with patent 
rights to the Army, Navy, and Police Force. Except 
as connoting the routine of one person telling or 
showing something to another, it means nothing and 
leads to nothing. Education implies understanding 
and a training of the faculties including the practical 
instincts. Instruction alone is useful for those who 
do not want to be, or are incapable of being, educated ; 
but matriculated students, such as one now finds in 
agricultural colleges, ought to be anxious for, and 
capable of, some education. ’ 
In the tropics, the so-called agricultural education 
A 
youth has been instructed how to read a polariscope 
or do a Babcock test—and becomes a chemist ! 
Another is taught to bud oranges or run a sugar mill, 
and becomes a planter. This has suited the tropical 
temperament and climate, and in most cases, it is to 
be feared, the average type of mentality. But if 
tropical agriculture is to advance we must aim at, 

