The Spectroscope and the Microscope. 303 



similar disks on either side of it, and then a small shutter, 

 worked by another screw, diminishes the length of the slit 

 to any extent required, and the blood disk, or other minute 

 object, is seen in a little optical cage, which shuts out the 

 view of other bodies. The prism is then replaced, and if 

 all the adjustments are in order, the absorption bands produced 

 by blood are distinctly seen. We have found it easy to 

 operate in this way with an object-glass as high as Smith and 

 Beck's Jg-th. 



Very important results may arise from Messrs. Huggins's 

 and Wenhanr's micro-spectroscopy of opaque objects. With 

 a two-thirds or half-inch objective it is easy to get a good 

 spectrum from a portion of blood dried on a card or a bit of 

 glass, and not bigger than a full stop in small print. A similar 

 portion of dried blood may be viewed conveniently with higher 

 powers as a transparent object. 



We reserve for another occasion a description of some in- 

 teresting experiments which will illustrate the kind of inquiry 

 for which the application of the spectroscope to the microscope 

 is adapted. Solutions and fluids of various kinds may be 

 placed in small cells, or, as Mr. Slack pointed out at the 

 Microscopical Society, minute drops of various substances may 

 be placed upon a glass stage and their spectra examined before 

 and after reagents are applied. The small drops required can, 

 as he explained, be handily taken up by glass rods drawn out 

 to the thickness of a needle, and having a little crook at the 

 end. The glass stage should have the bottom ridge turned in 

 at an acute angle, and glass sides, by which means the fluids 

 are prevented from escaping on the stage. Unless very small 

 drops are placed on this glass stage they run down too easily 

 and spoil the experiment. 



Mr. Browning deserves great credit for the skill displayed, 

 both in the invention and construction of this new and very 

 elegant spectroscope, which is exceedingly easy to use, though 

 a little complicated to describe. 



We append a view of this spectroscope, with a description 

 of the parts, so that our readers will find no difficulty in apply- 

 ing it to their microscopes. 



A is a brass tube carrying the compound direct vision 

 prism. 



B, a milled head, with screw motion to adjust the focus of 

 the achromatic eye lens. 



0, milled head with screw motion to open or shut the slit 

 vertically. Another screw at right angles to 0, and which 

 from its position could not be shown in the cut, regulates the 

 slit horizontally. This screw has a larger head, and when once 

 recognised cannot be mistaken for the other. 



