1872.] Microscopy. 121 
Some microscope lamps have lately been constructed in which benzoline is 
employed as fuel. This liquid possesses the advantage of being much cleaner 
in use than paraffine, the leakage of which very penetrating fluid is always a 
source of annoyance to those microscopists who have to carry a lamp from 
place to place. The lamps are very small and compact, and are well adapted 
for illuminating the achromatic condenser directly without using the mirror, 
a mode of lighting preferred by many of our best observers. There is no 
doubt that when the burner is properly adapted for the consumption of 
benzoline, a light approAching in intensity and whiteness that of camphine 
may be expected. Inthe few experimental lamps at present made, burners 
like those for the combustion of paraffine have been used, and consequently 
the quality of the light is much inferior to that which the fuel is capable of 
yielding. A lamp giving a very small intense flame and requiring but little 
attention is a desideratum. The camphine lamp is perfection in every respect, 
but the care required to keep it in order is an impediment to its very extensive 
use. 
Dr. J. J. Woodward has succeeded in producing some fine photographs of 
histological preparations by means of sunlight. Hitherto preparations of this 
kind, stained and injected, have yielded very inferior impressions by daylight, 
illumination with the lime, magnesium, or electric lights having given better 
results. The light enters the dark room through an achromatic lens of 
2 inches diameter and about ro inches focus, instead of the usual aperture, 
and is received upon the achromatic condenser after diverging from the focus. 
This illumination appears to have remedied the inconvenience caused by 
diffraction and interference, which in former experiments caused great confu- 
sion in the image. The low powers used in photographing these preparations 
giving in most instances an almost instantaneous picture, Dr. Woodward 
has contrived a means of regulating the exposure by a simple mechanical 
contrivance, and for these rapid impressions has managed to dispense with 
the use of the heliostat. A series of nine photographs, illustrating the capa- 
bilities of the process, has been placed in the collection of the Royal Micro- 
scopical Society. 
Mr. H. J. Slack has continued his observations on deceptive appearances 
presented by objects under the microscope. Some specimens of fine ruling on 
glass and steel by Mr. J. F. Stanistreet, F.R.A.S., executed by a simple machine* 
of his own contrivance, have furnished some singular results, which, as in former 
cases, point to the necessity of using the greatest caution in interpreting the 
results of observations on unknown substances. The objects supplied by 
Mr. Stanistreet consist of stars composed of bands of fine parallel lines, inter- 
secting each other as they approach the centre, and so forming a central star. 
When examined on a dark ground with powers of 3 inches to 3 inch, the 
idea of the rays standing up obliquely from the plane of the glass like the rays 
ofa fan is suggested, the apparent slope being varied as the stage with the 
objec is caused to revolve. Under a slight variation of the lighting, the inner 
star caused by the intersection of the bands can be made to appear in a higher 
plane than that of the primary star. The circular unengraved space in the 
centre has the appearance of a deep hole; as in former instances, the eye is 
perfectly satisfied with the focussing, which gives the appearance of the lines 
being in different planes. In another star composed of radial lines, those 
most brilliantly illuminated appear to stand above the rest. Complicated 
patterns, in which the intersections are more numerous, viewed with a % inch 
and Beck’s vertical illuminator, give at the most satisfaGtory focus the appear- 
ance of solid threads to the lines, one under the other at the simple inter- 
sections, and a tendency to make the spots of complicated intersection appear 
higher than the rest. With a one-fifth and Powell and Lealand’s modification 
of Professor H. L. Smith’s vertical illuminator, the complex portions of the 
pattern are resolved, but with a decided suggestion that the cuts are elevations 
or threads laid upon a semi-transparent surface like white porcelain. 
* Mr. Stanistreet’s ruling machine is described and figured in the Monthly Microscopical 
Journal for December, 1871. 
VOL. II. (N.S.) R 
