550 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
A simple Geometrical Indicator for the Microscope.* — Dr. Pietro de 
Yescovi describes a new form of indicator which has the advantage over 
those in general use of great simplicity and general applicability to any 
Microscope. It consists of a simple system of four straight lines (see 
fig. 62), traced on the stage of the Microscope, which virtually intersect 
in the projection of the optical centre of the field of view in such a way 
that each line is at 45° to the next. 
Fig. 62. 
In order, with this system of lines, to mark and recover the position 
in a preparation of an interesting point, the slide is held firmly or 
pressed against a projecting piece on the stage and a light mark is made 
with ink at three points on three adjacent lines of the system. The 
point of interest can at any time be again brought into the field of view 
by bringing the three points marked upon the slide upon the three 
adjacent lines of the system. 
The author would recommend Microscope-makers to engrave this 
system of lines on the stages of their instruments in white and red 
alternately on a black ground. 
Friedrich, P. — Eine Heizvorrichtung des Mikroskopes zu bakteriologischen 
Untersuchungen. (On a Heating Arrangement for the Microscope in Bacterio- 
logical Investigations.) 
Arb. a. d. k. Gesundh.-A ., VIII. (1892) No. 1, pp. 135-9. 
* Zool. Anzeig., xv. (1892) pp. 203-5. 
