1880. ] Microscopy. 691 
the utmost cannot exceed twenty miles, consisting of an entirely level flat, and prob- 
ably of alluvial soil. The level of the Chad and that of the river Binué, near Gewé, 
where it is joined by the Mayo Kebbi, seems to be almost identical; at least accord- 
ing to all appearance, the Binué at the place mentioned, is not more than 850 or 900 
l of th 
regular 
14th of September, would be explained by the draining of the waters through the 
Mayo Kebbi, caused by the highest rise in the Chad, which occurs in August. This, 
taken with the vast volume of the water which the rivers pour down, flooding the 
land for miles, seems to show its connection with a great system. 
“ Important results to the continent of Africa might follow an effort carefully made 
to rectify the apparent irregularities of the Shary. If only a portion of the enormous 
olume of water which is now absorbed and evaporated in the vast expanse of Lake 
ad were turned into the Binué, through the Mayo Kebbi, not only would such 
Steamers as the Henry Venn have access to that great lake, but they could probably 
ascend the Shary and Welle almost up to the territories of Munza, King of the 
Monbuttu.”’ 
Meteorological observations were taken on the Henry Venn four 
times during the day. There were no night records. Owing to 
the steadiness of the atmosphere, the daily variations of the 
barometer never amounting two-tenths of an inch when the 
vessel was at anchor, the approximate elevation of the highest 
point reached may be stated with some approach to accuracy at 
624 feet above the level of the Niger at Lukoja. 
_ This makes the average fall of the river to its mouth fifteen 
inches per mile. ‘ | 
€ maximum of the thermometer was 91°, and the minimum 
74°. The daily range amounted to only 3°. The average tem- 
perature for the whole period of eighty days was 79°. The ther- 
mometer did not rise to 80° in fifty-four days, and only reached 
75. in nine days while the highest point was only attained once. 
Rain occurred on twenty-eight days and lightning on twenty- 
one days. : 
MICROSCOPY .' 
Hotman’s New Compressorium Anp Morst CHAMBER.?—In 
working with living animal forms suitable for the elucidation of 
Some of the principal doctrines of life, any contrivance which will 
render the study easier, and hence more profitable and economi- 
cal of time, should be hailed with delight by the working micro- 
Scopist. Such a labor-saving device is represented in the accom- 
panying cut, Fig. 1, of Mr. D. S. Holman’s new compressor. 
This apparatus differs from all other compressors in being so 
arranged that the mica cover is fixed and immovable, while the 
lower, thicker plate of glass is moved up and down by means of 
a Screw nut and spiral spring, an arrangement which enables the 
student to adjust the apparatus so as to apply with certainty any 
gree of pressure upon any soft object without risk of breaking 
large and expensive cover glasses, crushing the object unex- 
! This department is edited by Dr. R. H. Ward, Troy, N. Y. 
* Advance sheets from Journal Franklin Institute for August, 1880. 
