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On the "Micro-megascope." 

 By John Matthews, M.D., F.R.M.S. 



(Communicated February 28th, 1879.J 



Mr. President and Gentlemen, — I must confess to a consider- 

 able amount of reluctance to occupy the time of the meeting at this 

 late hour, and after the very admirable and lucid lecture to which we 

 have been listening. I will try, therefore, to explain as briefly as 

 possible, the nature of the apparatus now before you, and perhaps 

 the best way of introducing the subject may be to give you some 

 idea of the course of reasoning which has led me to its construction. 

 Within the last year or two I have been studying the mode of for- 

 mation of, as well as the conditions which contribute to, the optical 

 images produced by lenses, and one amongst other experiments I 

 have tried is, whether the spherical dots (areolations ?) on the frus- 

 tules of certain diatoms, would give images of objects suitably placed 

 before them, in the same manner as the lenses in the cornea of an 

 insect. I found that they did so. I then tried various corneas and 

 diatoms, and as each afforded images varying in size only, and 

 perhaps in definition, when examined by the same power, it next 

 occurred to me that if I were to use a single and more perfect lens, 

 a larger as well as more distinct image would be obtained. I there- 

 fore placed an ordinary objective — by means of a suitable adapter — 

 and having its front combination upwards, either in the substage or on 

 the ordinary stage, as might be most convenient.* I then found that I 

 got a very perfect image of any object to which it was directed, 

 when it was examined by the objective in the usual place on the 



* Since the above communication was made, I have been informed, and 

 have satisfactorily ascertained, that Drs. Curtis and Ward, of the United 

 States of America, devised a very similar arrangement, and published it in 

 the "American Naturalist" for Nov. and Dec, 1870, and Sept., 1871. 

 Extracts from their papers will be found in the " Monthly Microscopical 

 Journal " for 1871 and 1872. The method of application was in both cases 

 somewhat ambiguous. — J.M. 



