SnLUunerim'] I^oijol Microscopicd Society. 281 



II. — Reminisceyices of the Early Times of the Achromatic Micro- 

 scope. By J. S. BowERBANK, LL.D., F.E.S., F.E.M.S., &c. 



(^Bead hefore the Eoyal Microscopical Society, May 11, 1870.) 



The excellent annual address of your President, and the accom- 

 panying interesting Memoir of the late venerated J. J. Lister by 

 his son, Professor Lister, of the University of Edinburgh, published 

 in the ' Monthly Microscopical Journal,' renders quite superfluous 

 any attempt, on my part, to detail the early history of the improve- 

 ments of the modern achromatic microscope. I shall therefore re- 

 strict my communication to the reminiscences of its early apphcation 

 to scientific investigation. 



My first introduction to Mr. WilHam Tulley was in 1828, at 

 the house of a friend to whom he was showing some of his favourite 

 test objects ; and before we parted that evening he had kindly en- 

 gaged to make me such another instrument as the one through 

 which we had been looking. Shortly afterwards, as he was unable, 

 from press of other business, to complete my instrument, he placed 

 in my hands his own, and the original combinations with which to 

 work until he could complete the one ordered by me. He told me 

 that but four such as I had ordered had been made, and that they 

 were in the hands of Mr. Lister, Dr. Birkbeck, Lord Ashley, and 

 himself. Dr. Birkbeck's instrument, after the decease of that gentle- 

 man, passed into the hands of my late friend, Mr. George Loddiges, 

 and from that time forward, until his death, we worked together in 

 concert. Every new improvement in combinations by Lister, Boss, 

 and Powell, were examined carefully and critically by us ; with Mr. 

 A. White and Mr. J. Page we measured their angular apertures, and 

 tested their centering and definition with minute globules of mer- 

 cury, and other test-objects, and so did our best to incite the makers 

 to aspire to the greatest possible perfection in the construction of 

 their object-glasses. As the object-glasses increased in power and 

 perfection, we found it necessary to increase the steadiness of the 

 brasswork. Many anxious consultations were held on this part of 

 the subject, and numerous experiments were tried. In this branch 

 of our endeavours at improvement we received important assistance 

 from our late talented friend, Mr. Jackson, to whose mechanical 

 genius and practical dexterity as a workman we are in a great mea- 

 sure indebted for the admirable stabihty of the best of our modern 

 instruments. The solid bar, with a rabbited groove, carrying the 

 body and stage on one mass of metal, and the rabbited grooved 

 stage, were the inventions of that able mechanic. The first mount- 

 ings of this description, after the construction of his own instrument, 

 were ploughed by Mr. Jackson for my new microscope, with his 

 beautiful little ploughing machine ; the remainder of the work was 



