440 General Notes. [July, 
Survey an interesting sketch of the mode of carrying on the geographical 
work of the Survey, showing the evidence on which the final maps prepared 
by the Survey rest. The primary triangulation was in charge of Mr. 
James T. Gardner until the autumn of 1875, when, on his resignation, the 
work was continued by Mr. Wilson. To give some idea of the amount 
of work that has been done by the topographical corps in the Survey of 
Colorado, it may be stated that it has established 1280 topographical 
stations within an area of about seventy thousand square miles, and from 
each station all the surrounding country was sketched. Mr. Wilson’s 
assistant made over one thousand pages of profile sketches during the 
field season of 1875, each page being six by ten inches, while he himself 
made some five hundred pages of drainage sketches, and took the thou- 
sands of angles that were necessary to locate all the points. The high 
order of the work done, added to the difficulties and dangers under which 
geographical labor is performed in the most mountainous and wild sec- 
tion of our country, reflects credit upon our government in authorizing 
and sustaining such undertakings. : 
GEOGRAPHICAL News. — The Geographical Magazine is publishing 
an account of the Official European Cartography in 1875-76, which 
possesses a good deal of interest. Among recent books of travel are 
Cameron’s Journey across Africa; Canoe and Camp life in British 
Guiana, by C. Barrington Brown; The Cradle of the Blue Nile, by 
E. A. De Cosson; Peru in the Guano Age, by A. J. Duffield. Baron 
von Richthofen’s new work on China is ready for publication. Au erup- 
tion of Mauna Loa, the great volcano of Hawaii, took place on February 
14th, in a new district. The lava probably came from the summit-rent, 
and traveled to the coast by subterranean passages. 
MICROSCOPY.! 
ZENTMAYER’S TURN-TABLE. — Mr. Zentmayer has recently contrived 
a turn-table on which the slide is self-centred for width, by the absurdly 
simple device of bringing its two sides up to the opposite sides of a 
couple of brass pins equally distant from the centre of rotation. The 
adjustment for length is made by hand, guided by circles on the brass 
plate, or for slides of standard size by a pin at one end. The slide may 
be of any reasonable width, and can be easily and instantly decentred 
for refinishing old slides. The table is mounted with a clamp for attach- 
ing it to a table, though it can be furnished on a heavy block in the 
usual manner, if desired. : 
Microscopy ar NAsuviLLeE. — At the Nashville meeting of the 
American Association for the Advancement of Science, commencing Au- 
gust 29th, and continuing about one week, special arrangements will 
be made for the care of instruments and for the convenience of thor : 
_ who wish to use them. The local sub-committee having charge of these 
-arrangements consists of Dr. T. O. Summers, Jr., and Profs. G. S. Blackie 
- 3 Conducted by Dr. R. H. Warp, Troy, N. Y. 
