MICROSCOPY. 503 
init. I should not have noticed this, had not Mr. W. unfairly, 
as I think, charged me with a misstatement. 
Next, Mr. Wenham couples C. S. and Mr. Bicknell together as 
if they acted in concert, and were joint writers. I can assure 
Mr. Wenham that it is not so. Mr. B. is not responsible for any 
thing I have written, nor am I for him. Neither had seen ‘the 
other’s writing until it was public. 
Next, I have no “ plea or atonement” to make “for expressions ` 
hastily or inconsiderately written.” My expressions were used 
deliberately and after full consideration of their import. :I still 
hold the same opinion, namely, that selling an objective by a name 
that does not approwimately indicate its focus (i. e. 4 for 4, 2/5 for 
ts or, as I have known, sẹ for gy, as in the case of an eminent 
French maker ; or, as in another instance, a jẹ for a zy; OF, as in 
the case of an English objective that I have recently heard of, a 
A zy for a 4) is an “ imposition,” or a fraud if that term is preferred, 
A not applying it, however, as Mr. Wenham represents, to a partic- 
ular firm, but to all, of any country, who practise such “ impo- 
sition ;” and that Mr. Wenham in his paper, by stating that “ {ths 
Were 4ths or +1,ths, and some now approach 7yths in power,” with- 
out disapproval, was practically defending the custom, and that he 
does not now deny. His paper in reply to Mr. Bicknell was pub- 
lished in December. In May he writes, “ no one knows better than 
myself the difficulty of adopting a nomenclature that shall exactly 
denote the power of all the highest object glasses sent out”—some- 
: thing has evidently produced some effect on him since that time. 
The complaint was not of want of “ exactness,” but of gross mis- 
namers of twenty or fifty per cent., such as he named in the De- 
r paper, not in regard to the highest powers alone but 
applicable to the lowest powers as well. Such was what I called 
àn imposition, and I call it so now. 
In the “ Quarterly Journal of Microscopical Science,” October 
1862, Capt. Mitchell gives the measurement of the focus of several © 
London objectives; most of them being undernamed. Capt. M. 
complains of this; he says “ when I buy a 4th, I want a 4th, not 
Something else.” He calls those correctly named, honest ; by im- 
Plication, those not so named, dishonest. 
a Wm. B. Carpenter (“The Microscope,” fourth ed., 1868, p 
í Says, “the designations given by the opticians to their objec- 
ves are often far from representing their focal length, as esti- 
mated by that of single lenses of equivalent magnifying power, & 
