Olservations on Periscopic Spectacles. 465 
tive and negative attributes, they snatched up a plane tool 
and with barbarous whirls annihilated periscopic. Mon. 
Cauchvix must not do so; for he no doubt expects to get 
some money by the lunettes a la bombée, as well as Dr. W. 
for his a la periscopique. 
As I prefer amity to a difference with a French philoso- 
pher, I shall dispense with adverting to what I know to 
be M. Biot’s errors and illusion, He must allow me one 
remark, that is, that his countrymen should witness a per- 
fectly fair experiment of a comparison between the double 
convex and his adopted meniscus form of glasses, for me- 
niscus, periscopic, and Lombée, are synonymous terms. 
There will also be e xpected from him a mathematical or 
geometrical demonstration of the superiority of the form he 
has pledged himself to; for Dr. W. on his part has not 
been able to produce any mathematical demonstration what- 
ever. But how is it that Dr. W. for these seven years 
past has not called to his aid some competent professor or 
tutor from the university in which he has studied to be his 
champion of interest ? he surely knows that there are se- 
veral both at Cambridge and Oxford, quite able to decide 
upon our trivial scientific question. Is there no one 
among his mathematical friends (and constant attendants 
at the honourable Society to which he is Secretary) willing 
to be an English evidence of his discovery and a witness to 
the surprising fic ld of mew gained by the menisens? Is it 
by a foreigner only that the interest of his cause is to he 
espoused maintained and propagated? fn my defence of 
the double convex lens, I possess an indubitable authority 
among others of a declaration by that date excellent! optician 
Dr, Maskeline, that Dr. W’s torm of lens of ihe meniscus 
kind is the worst of all others for any optical purpose what- 
soever ! 
I could adduce something still stronger and more conclu- 
sive; but, really, sir, lam ashamed to trespass any further 
on the patience of your readers, and take up more pages of 
your valuable Journal. Enough is already before the public, 
to produce by an easy experiment a full conviction of the 
truth. I continue, 
y Sir, 
Your respectful and obedient servant, 
Holborn, Dee. 15, 1813. Ww. JongEs, 
Vol, 42. No. 188. Dec. 1813. Gg LXXVI. Re- 
