Marcu 25, 1915] 
NATURE 
105 


melting temperatures, of the materials used in the 
glass mixtures, and leave the contents of the pot un- 
contaminated at the conclusion of the operation. This 
research would probably be a long and costly one, and 
is such as might most appropriately be undertaken by 
the National Physical Laboratory, especially as certain 
details in the manufacture of optical glass may come 
under review during the inquiry. 
Authoritative Testing of Glass. 
(5) In another direction evidence was submitted to 
the guild to the effect that it would be distinctly advan- 
tageous to the optical trade if increased facilities for 
the authoritative determination of the optical con- 
stants and relative absorption of samples of glass 
submitted for test could be provided at the National 
Physical Laboratory 
THE FUTURE. 
Facilities for Education a Matter of Great Urgency. 
(6) In still another direction evidence, additional to 
evidence collected before the outbreak of hostilities, 
was elicited that the facilities for education in technical 
optics are very inadequate. It was shown that not 
only could some of the present difficulties connected 
with the supply of optical glass probably be diminished, 
but that the output of optical instruments for national 
purposes would be increased, and that the optical trade 
would be substantially benefited in other directions 
if such facilities were largely extended. The Technical 
Optics Committee of the guild was originally ap- 
pointed, early in the year 1914, for the purpose of 
“inquiring into the need of an Institute of Technical 
Optics and the steps to be taken in connection there- 
with, and in due course it submitted a ‘‘statement”’ 
on the subject, which was published in the annual 
report of the guild, 1914, pp. 31-34. The committee 
had further reported to the Executive Committee of 
the guild at its July meeting, and the report was 
adopted with a few alterations, and is printed at the 
end of this report. 
(7) When the Technical Optics Committee met after 
the vacation, the other matters, apparently of more 
immediate urgency, referred to in this report, had 
arisen and took precedence of the earlier matter. In 
investigating these new questions it has become 
strongly evident that the earlier matter is of supreme 
and pressing importance. 
The guild therefore recommends :— 
(A) That better provision should be made at the 
National Physical Laboratory for the testing of samples 
of glass as to their physical and optical properties, 
and that the director of the National Physical Labora- 
tory be approached on the subject. 
(B) That facilities should be provided as speedily as 
possible for the carrying out, at the National Physical 
Laboratory, or elsewhere, of the researches connected 
with the manufacture of optical glass referred to in 
this report. 
(C) That steps should be taken as speedily as pos- 
sible to give effect to the recommendations of the 
previous report of the Technical Optics Committee of 
the guild in the direction of providing facilities for 
systematic, scientific, and manual training in technical 
optics, and the guild, recognising that educational 
training requires time, is strongly of opinion that this 
question is urgent and that the organisation of optical 
training should be taken in hand at once. 
PREVIOUS REPORT REFERRED TO IN PARAGRAPH C, DATED 
JULY 14, I914. 
Proposed Establishment of an Institute for Technical 
Optics. 
The British Science Guild has had under considera- 
tion for some time the inadequate provision for, and 
NO. 2369, VOL. 95| 

the unsatisfactory state or, the technical training in 
optics in the British Isles. The subject was brought 
to its notice by Sir Thomas Barlow, formerly presi- 
dent of the Royal College of Physicians, in a com- 
munication to the president of the guild, and was 
considered to be of such importance by the Executive 
Committee that a Special Committee was formed to 
deal with it. The Special Committee has now. re- 
ported. 
The establishment of such an institute has been 
under discussion for some years, and there is a re- 
markable consensus of expert opinion, both as to the 
necessity and the urgency for action, from many and 
diverse points of view, scientific, industrial, and 
national. 
The London County Council, which has gone into 
the matter very thoroughly, has not felt itself in a 
position to provide from the funds under its control 
the initial capital expenditure of some 40,000l. for the 
erection and equipment of the proposed institute, 
although a site was actually purchased for the very 
purpose by the governing body of the Northampton 
Polytechnic Institute so far back as 1g08. The 
Finance Committee of the council is understood to be 
of opinion that the project is so essentially of national 
importance that it would be unfair to saddle London 
ratepayers with the whole cost. It is, however, be- 
lieved that if the question of capital expenditure can 
be solved, the maintenance of the institute could be 
assured by grants from the Board of Education and 
from the London County Council, and by students’ 
fees. As an additional reason for expedition, it may 
be pointed out that the governing body of the North- 
ampton Polytechnic Institute may not be in a position 
to carry much longer the heavy burden of the mort- 
gage interest on the purchase money above referred 
to, and the amortisation of the capital amount. 


GEOLOGY IN RELATION TO THE EXACT 
SCIENCES, WITH AN EXCURSUS ON 
GEOLOGICAL TIME. 
T is often said that figures can be made to prove 
anything; and certain it is that a series of arith- 
metical operations does sometimes serve as introduc- 
tion to very strange conclusions. The fault, of course, 
is not in the tool, but in the hand that uses it. In the 
larger issues of geology especially, where the gulf to 
be bridged between data and conclusions is so often a 
wide one, ingenuity of reasoning ought surely to be 
accompanied by a due sense of responsibility in the 
handling of figures. Calculation, in such applications, 
is by no means so simple an art as it may appear. In 
wrestling with problems of the kind indicated, and, I 
must add, in reading some very fascinating specula- 
tions by geologists of high standing, I have often 
wished that some obliging mathematician would put 
forth a small manual of applied arithmetic for the 
guidance of workers in the descriptive sciences. There 
are absolutely necessary precautions to be observed 
when calculation is based upon data always partial 
and at best roughly approximate, and these pre- 
cautions are too often neglected. To be safe, we must 
have some conception of the probable error attaching 
to our observations, and we must note how the initial 
errors may be multiplied in the process of calculation. 
Especially there is the cumulation of error which must 
ensue when results obtained in this fashion are used 
as links in a chain of deduction. Here it is quite 
inadequate to say that the chain is no stronger than 
its weakest link; it is of necessity far weaker than 
its weakest lini. 
1 From a Presidential Address delivered before the Yorkshire Geological 
Society by Alfred Harker, F.R.S. Reprinted from the Proceedings of the 
Society. 
