: a 
J.J. Woodward on Nobert’s Test-plate. 169 
two or three to thirty per minute, and averaging nearly 500 
stars per hour. When several stars present themselves almost 
at the same instant, I have preferred, rather than to omit any 
of them, to divide the error of right ascension and to ma 
them as rapidly as possible. Usually by predetermining the 
order of mapping, I can map six or eight stars in quick suc- 
cession, without an error exceeding two seconds. When the 
paper reaches the end, a spring constantly pressing upon it, 
locks into the star-key, and thus indicates the conclusion o 
the map. 
It may not be improper for me to add briefly my reasons for 
not having before described my invention in the columns of 
magnitudes of the stars observed should be recorded ; an 
decided to defer the publication of the description of the star- 
mapper until I should be able to publish in connection with it 
a description of my Photo-mapper. With your permission, I 
will, in your next number, proceed to deseribe this latter in- 
strument. : 
Art. XVIL— Additional remarks on the Nineteen-band Test- 
plate of Nobert; by J. J. Woopwarp, Asst. Surgeon and 
Brevet Lieut.-Colonel U. §. Army. Contributed by permis- 
sion of the Surgeon General. 
Iy a former paper in this Journal (II, vol. xlvi, 
I gave an account of certain observations le 
nineteen-band test plate of Nobert with various len 
nses. The 
_ Seneral result of these observations was, that, with the ,';th 
Anu Joun bo : 369. 
UR. Sci.—Szconp Serres, Vou. XLVIII, No. 143.—Sepr., 1869. 
a 3 12 age 
