THE 
MONTHLY MICROSCOPICAL JOURNAL. 
DECEMBER 1, 1869. 
I. — Further Remarks on the new Nineteen-hand Test-^late of 
Nohert, and on Immersion Lenses. By J. J. Woodward, 
Assistant-Surgeon and Brevet Lieutenant-Colonel U.S. Army. 
Contributed by permission of the Surgeon-General. 
{Read hefore the Koyal Microscopical Society, Cdober 13, 1869.) 
(Communicated by Jabez Hogg, Hod. Sec.) 
The ' Quarterly Journal of Microscopical Science' for October, 1868, 
contains (p. 225) a short article in which I record the results of 
certain experiments made by me with the new nineteen-band test- 
plate of Nobert. In that paper I stated that I had obtained the 
best results with the -^^ih. objective of Messrs. Powell and Lealand, 
of London. The sVth of these makers, which in my hands had 
excelled their -^^ih on Podura and other test-objects, proved inferior 
on this plate, apparently because the cover of the object was too 
thick to allow the lens to do its best. With the aVth I satisfac- 
torily resolved the true lines of the fifteenth band of the plate ; and 
subsequently my friend and assistant, Brevet-Major E. Curtis, 
Assistant-Surgeon U.S.A., prepared a series of photographs of the 
several bands, showing the true lines in each, from the first to the 
fifteenth inclusive. I was, however, unable to make out the true 
lines in the last four bands with any lens then in my possession. 
I conceived the idea, nevertheless, that if I could procure a test- 
plate ruled on a thinner cover, so as to give the ^^th full play, I 
might go farther. I therefore wrote to Fobert, who, after long 
delay, furnished me with a new test-plate, wmcn reached me during 
March of the present year. This test-plate cannot be too highly 
praised for its delicacy and beauty. The lines are ruled on the 
under-surface of a square of thin glass the ^Isth of an inch thick, 
which is cemented to a glass circle the tto th of an inch thick. This 
circle is mounted over a round aperture in a strip of burnished 
brass 3 inches by 1, on which is inscribed the usual memoranda 
placed by Nobert on his nineteen-band plates. 
VOL. II. X 
