302 The Spectroscope and the Microscope. 



same paper the application of the instrument to opaque objects 

 was also pointed out, and Mr. Wenham, who stated that he 

 had assisted Mr. Huggins in some of his investigations, said, 

 "We so far differ from Mr. Sorby that we are able to make 

 an analysis of the smallest microscopic object, such as the 

 smallest portion of a blood disk, mounted in the ordinary way. 

 We can get a strong spectrum, and the power of the object- 

 glass gives a better result We found some 



curious results from investigating opaque objects. In all 

 spectrum analysis the difficulty is to get a monochromatic light. 

 Generally we get a spectrum of some sort; but from the 

 surface of many opaque objects the reflected light is perfectly 

 monochromatic''' 



At -the meeting of the Society, at which the preceding 

 remarks were made, Mr. Slack stated that he had tried a direct 

 vision spectroscope made by Mr. Browning for Mr. Gassiot, 

 and that an instrument of this description would be convenient 

 for use with the microscope. Mr. Browning had already 

 turned his attention to this matter, and after many experiments, 

 in some of which we believe Mr. Sorby took part, he devised 

 a compound prism, giving direct vision, and haviug an amount 

 of dispersion very well adapted for the exhibition of delicate 

 absorption bands. 



The new spectroscope for the microscope may be used under 

 the stage, when required ; but its most convenient place is that 

 of an ordinary eye-piece. As will be seen from the figure sub- 

 joined, it is a very compact piece of apparatus, very ingenious 

 in construction, and consisting of several parts. The prism 

 is contained in a small tube, which can be removed at pleasure. 

 Below the prism is an achromatic eye-piece, having an adjusti- 

 ble slit between the two lenses ; the upper lens being furnished 

 with a screw motion to focus the slit. A side slit capable of 

 adjustment admits, when required, a second beam of light from 

 any object whose spectrum it is desired to compare with that 

 of the object placed on the stage of the microscope. This 

 second beam of light strikes against a very small prism suit- 

 ably placed inside the apparatus, and is reflected up through 

 the compound prism, forming a spectrum in the same field 

 with that obtained from the object on the stage. 



Mr. Wenham pointed out the importance of so far modify- 

 ing Mr. Huggins's plan as to allow any small object to be 

 brought into the field and focussed in a convenient way. In 

 Mr. Browning's plan nothing is easier. The prism is taken off 

 and the slit opened by turning a screw. The apparatus then 

 acts simply as an eye-piece, and a single blood disk may be 

 brought exactly in the middle of the field. The spectroscope 

 slit may then be closed so as to isolate the blood disk from . 



