994 General Notes. [September, 
carriers, including their- accessory parts, namely, the knife and 
object. Fig. 2 gives a more precise idea of the details of con- 
struction 
In the figure the lower spear of the carrier æ, which sup- 
e knife, show three prominences, 
tas gives the geometrical projection 
of the five points, Within the — 
the figure these points could not be — 
drawn exactly as they are in the aan 
ment itself. In reality they appear only 
r 
the stand. This arrangement was : 
rable to facilitate the action of the oil $ 
Fic. 2,—Tr. Pi ea of p with which the sliding surfaces are to : 
tux ene a be covered. Two of the ridges form — 
carrier for the knife; b carrier er together parts of the oblique plane, and ie 
Ta the object ; d, screw t attach the third catepan to the vertical Ei 
Naples deak 8 e siqing plane. The same arrangemeti 
s found in ro carrier 4, which sup- 
ports the clamp in which aie object is placed. a 
By this mode of construction the carriers will move gently and ve 
eeoa even if the sliding surfaces on the stand are not 
geometrical planes. It is still, however, of course desirable that & 
much exactness as possible should be obtained in these Pee 
their irregularities cannot fail to affect the sections, especi 
they are in fact multiplied in the latter. Professor Thoma highly 
commends Herr Jung, of Heidelberg, who makes the ni ae : 
under his instructions, for the great exactness which he has 
tained ee 
As the efficiency of the newly-constructed instrument is best 
judged of by practical experience of its gee Professor 
Thoma peene og generally that it bas been d tha stone 
micro- 
1 Professor biring oe that at a time when already a number se Sag 
tomes were in use, an instrument entirely different in its ponn Pe aa) 
constructed on sition principles, appeared in America—the m P pper id 
; y i 
rgi: 
dence a the invention is on both sides very evident. The value of w have 
however, is at the same time el isted by the relative good re aimee 
been otheined by this American meae Its limit as regards the H 
sections appears to be 0.0004 in 
