fou°nll.\';Mi7chnm] Boyal Microscopical Society. 135 



■/o and xV it is so shown only in a small portion of the field near 

 the centre, and in the rest has a bur shooting outwards." This bur, 

 of which a sketch is given, is the first mention of the "coma" 

 which afterwards formed so important a subject of his investigations. 

 The note goes on to describe a suggestion for another combination, 

 illustrated by drawings of magnified views of the curves of the 

 glasses, executed with his usual extreme neatness and accuracy ; 

 and it concludes with the words " tried many experiments to ascer- 

 tain the best means of correcting small errors in aberration." 



The note from which these quotations are made is the first of 

 a long series of accounts of experiments, with remarks upon them, 

 indicating an amount of labour of which, as I never saw the papers 

 before, and as the work was for the most part done either before 

 my birth or during my early childhood, I had previously had no 

 idea. The notes are beautifully arranged and might well be pub- 

 lished just as he left them. I must, however, content myself with 

 mentioning, in chronological order, some of the most interesting of 

 their contents. 



In 1826, after a description of Amici's reflecting microscope and 

 an account of its performance, I find further projections of object- 

 glasses for Mr. Tulley, followed by a di-awing for the engraver to 

 illustrate a description of Tulley 's microscope, published by that 

 optician. A copy of this pamphlet has been preserved, and the 

 first page begins with this acknowledgment : — " Before commencing 

 the description of the microscope it will be proper to state that the 

 construction of the instrument and its apparatus was suggested and 

 made from original drawings by my friend, J. J. Lister, Esq., 

 whose ingenuity and skill in these matters are very generally 

 acknowledged." The chief novelties in this instrument, besides the 

 improved object-glasses, were the following : — 



Graduated lengthening tube to the body. The stage-fitting 

 for clamj)ing and rotating the object. A subsidiary stage. A 

 dark well. A large disc, which would inchne and rotate for opaque 

 objects. A ground-glass moderator. A glass trough. A live-box 

 made with flat plate, A combination of lenses to act as condenser 

 under the object (apparently the first approach to the present 

 achromatic condenser). The erecting-glass ; and the adaj^tation of 

 Wollaston's camera lucida to the eye-piece. 



The value of the erecting-glass for facilitating dissections under 

 low powers is, perhaps, even yet not sufiiciently appreciated. 



The camera lucida had long been a favourite instrument with 

 my father for drawing landscapes : and I may add that the tripod 

 which he invented for supporting the drawing and the camera, is 

 that which is now universally used by photographers. 



In December of the same year occurs an account of an exami- 

 nation of a set of four plano-convex lenses, each consisting of a 



