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taking this extra trouble the operator will be sure of sharper results. For 
opaque objects I make use of an ordinary magic lantern reflector, to the back 
of which I have soldered a piece of brass tube, whioh glides upon another 
tube let into a turned wooden font. By receiving the rays from off the white 
cardboard, the object inclosed in the cell or otherwise can be equably illumi- 
nated, and, as the whole is all^connected together, any vibration is commu- 
nicated throughout the whole arrangement. With regard to the exposure 
requisite, the exuvia of spider, skin of caterpillar, leg of beetle, and the star- 
fish, were all done in open daylight, through an eighth- of-an-inch stop, in one 
minute and a quarter.” 
A simple, form of finder is now sold by Messrs. Baker, of Holborn, and 
from its ingenuity and comparative accuracy, is worthy of notice. It 
consists of a curved bar attached to the stand of the microscope, and moving 
on a horizontal axis. It is so contrived that when the surfaces of the stage 
(mechanical stage) are brought into their rectangular positions, and an object 
is in situ , it can be pushed down upon the slide. If the latter be covered 
with paper, the point of the bar leaves a slight puncture. All that is 
necessary, when it is required to examine the object in future, is to move the 
stage till the puncture on the slide comes under the point of the bar or 
finder. The object will then be in the centre of the field. 
A New Method of Illumination. — Count Francesco Castracane suggests a 
new method of examining microscopic objects, which may possibly be found 
useful by those engaged in the investigation of the lower plants and animals. 
The great difficulty which our microscope manufacturers have had to over- 
come is that of the correction of lenses for chromatic aberration. The 
ordinary continental objectives are rarely perfectly achromatic, and this is, of 
course, a great objection to their employment in cases where precision is 
required. Count Castracane proposes to neutralize this quality of inferior 
object-glasses by using light of one colour, which cannot be decomposed. 
His plan consists essentially in the employment of one of the component 
pencils of the solar spectrum made to fall upon the mirror of the microscope, 
and be thus reflected to the object. In his researches he employed one of 
Dubose’s heliostats, by which means he obtained a field wholly illuminated 
by coloured homogeneous light. — Yide The Lancet , Record of the Progress of 
Medical Science , October. 
Abstracts of papers relating to Histology will be found under the 
following heads : — 
Botany. — The Pollen Grains of Kanunculus. 
The Process of Fructification in Sphserise. 
Spiral Vessels. 
Plants within Plants. 
The Vitality of Yeast. 
Medicine. — The Development of Muscular Fibre. 
Zoology. — The Development of the Axolotl. 
The Ooze from the Atlantic Cable. 
The Microscopic Anatomy of Hydrozoa. 
The Transformations of Chloeon dimidiatum. 
