432 
Scientific Notes. 
[July, 
Microscopy. — The “ Monthly Microscopical Journal ” of May contains a 
valuable paper by Mr. Thomas Palmer, B.Sc., “ On the Various 
Changes Caused in the Spe&rum by Different Vegetable Colouring 
Matters.” The paper is accompanied with several spedtrum charts, and con- 
tain*' a detailed account of the processes used in preparing the various 
colouring matters for examination, and also accurate measurements, reduced 
to wave lengths, of the positions of the various absorption bands. Mr. 
Sorby, in his remarks on the paper, stated that vegetable colouring matters are 
much more complex than is generally supposed ; most of them are undoubted 
mixtures of two or three kinds of matters, and even the chlorophyll, the 
green colouring matter alone, is composed generally of two green matters, 
which exist separately in certain plants. The line it would be most impor- 
tant to carry out would be, what were the chemical differences which gave 
rise to these changes in the spedtra. 
“ Notes on Inclusions in Gems, &c.,” by Isaac Lea, LL.D. This paper, 
published in the “ Proceedings of the Academy of Natural Sciences, Phila- 
delphia,” and reprinted in the “ Monthly Microscopical Journal,” vol. xvii., 
p, 198, may be consulted with advantage by all persons interested in this 
subjedt. It contains the history of the cavities in crystals and their contents, 
from the paper by Sir Humphry Davy, published in the “ Philosophical 
Transactions,” 1822, to the present time ; a full list of references is given, 
and it forms a valuable contribution to the bibliography of this interesting 
subject. 
An ingenious modification of the achromatic condenser has recently been 
constructed by Messrs. Beck. It consists of an achromatic combination 
mounted in the usual fittings ; over this slides a cylinder upon an eccentric 
rotating axis ; the disk closing the upper end contains a series of holes, 
which can be brought accurately one by one over the lenses of the condenser 
by the rotation of the fitting; these apertures carry a series of lenses, by 
which a modification of the illuminating pencil is obtained. Lenses, achro- 
matic or not, may be used to alter the aperture and focal length ; spot lenses, 
central or marginal stops can all be employed with the greatest facility, ren- 
dering the variety of illumination attainable almost infinite. 
A new and simple oblique illuminator has been contrived by the Rev. 
Lord S. G. Osborne, M.A., which he calls the “ Exhibitor.” The foundation 
consists of a “ Darker ” stage, as used for carrying selenite plates in 
polarising. Two counter sinkings are turned in the revolving ring, the top 
one rather larger in circumference and shallower than the lower one. Into 
the lower sinking is dropped a disk of blackened metal, with a small hemi- 
spherical lens mounted in the centre. Into the upper sinking are placed thin 
metal disks with certain apertuies made in them ; the front of these disks is 
just level with the face of the stage, the back close to the front of the disk 
holding the small lens. A fine screw is cut into the back part of the revolving 
ring, coming up just below the lower counter sinking ; into this screws a brass 
ring carrying anothei hemispherical lens of the full size of the aperture. The 
screw movement has a milled edge, permitting the distance between the 
lenses to be regulated. The apertures may be made as found useful ; one 
very successful consists of No. 1, a fine slit, in length about the aperture of 
the upper lens in the centre ; No. 2, a similar aperture a little way, say not 
quite its own length from the centre ; Nos. 3 and 4, a pin hole and a triangle, 
also a little out of the centre ; these may all be cut in one disk. On the 
stage there are two steel springs for holding the sides, giving the means of 
shifting them in any direction. Abraham’s achromatic prism is to be preferred 
to the mirror, and the flame of the lamp turned edgeways. 
