88 CORRESPONDENCE. 



the observer draws only what he thinks important, he must almost 

 invariably make a picture quite different from the one seen in the 

 microscope — he has. omitted what he deemed the unimportant parts — 

 and the pupil trying to follow him finds the actual appearance so dif- 

 ferent that he does not recognize it as the same. No doubt many of 

 the misunderstandings or differences of opinions among microscopists 

 have originated from this very defect of published figures, which have 

 been taken to be what they purported to be, representations of what 

 was actually seen — ' if his theories are correct '; but if his theories are 

 wrong, then his skilful delineation has only misled his readers. But 

 if the draughtsman publishes his figure as explicitly as his theory, not 

 as the representation of the ' severe fact,' then he will be understood. 

 On the other hand, the camera represents exactly what may be seen 

 by any other observer using the same appliances (which should in all 

 cases be described), and the student can draw his own conclusions 

 from the picture as to the soundness of the theories advocated. But 

 then it must be remembered that a photograph can represent only one 

 view of an object, while the observer, by changing the focus of his 

 instrument, obtains a new view at each movement of the screw. With 

 the high-power lenses now in use, these differing views are all im- 

 portant for correctly understanding almost any object. Therefore 

 scarcely anything can be properly illustrated by one photograph. 

 Many objects must require several." To which remarks the editors 

 reply : — This inflexible limitation of the photographic view to one sec- 

 tion or plane of the object is evidently one of the points referred to in 

 the criticism quoted above, which, without referring to photography as 

 a means of proof of alleged observations, or of submitting observations 

 to investigators for criticism or deduction, only suggested that for 

 communicating well-ascertained facts a skilful delineation may contain 

 more information than any available number of photographic repre- 

 sentations. A good drawing, as intimated by Dr. Beale, may often 

 supply the place of a long and unread verbal description. 



COKKESPONDENCE. 



Micro-spectroscope. 



To the Editor of the 'Monthly Microscopical Journal." 



Sir, — Mr. Gayer was probably not aware that the micro-spectro- 

 scope described by him is the same in optical construction as the 

 original form which Mr. Huggins explained, and figured in a paper 

 before the Society, May 18th, 1865. In this two equilateral prisms 

 of dense glass were used. I was present when the first investigations 

 were made with this instrument, which gave good results with the 

 highest powers and also on opaque objects. This was the first 



