58 



THE AMEPJCAN MONTHLY 



[March, 



be new, but I have never seen it figured or 

 described. Its advantages are obvious, and 

 I am sure every reader of the Journal 

 who will have this simple auxiliary fitted 

 to his turn-table will be pleased with it. 

 A. L. Woodward. 

 Syracuse, N. Y. 



THE ACME STAND. 



To THE Editor: — Referring to the 

 description of the " Acme " stand, which 

 appeared in the first issue of your Jour- 

 nal, I desire to add a few words in order 

 to place the matter fairly before your 

 readers. 



The " Acme " stand owes its appearance 

 to an agreement, entered into between 

 Prof. J. Edward Smith and myself, over a 

 year ago, while we were present at the 

 Microscopical Congress at Indianapolis. 



Without going into details, it was then 

 and there mutually agreed to attempt the 

 production of a new stand, which should, 

 at a low cost, comprise all the late im- 

 provements, be equal to any and all work 

 — in short, the idea was to produce, if pos- 

 sible, an Acme stand. Prof. Smith agreeing 

 to give the benefit of his long experience 

 as a manipulator, and I mine as a work- 

 ing optician. 



Our agreement has been carried out to 

 the letter, and from the date mentioned. 

 Prof. Smith and myself have been in close 

 correspondence, the result of which is the 

 "Acme " stand. 



Will you, as an act of justice, publish 

 this explanation, and with the hope that 

 the " Acme " will be found practically what 

 Prof. Smith and myself claim for it, I re- 

 main, dear sir, 



Respectfully yours, 



John W. Sidle. 



Philadelphia, January 25th 1880. 



NOTES. 



— The Iowa State Medical Society con- 

 vened at Des Moines, on January 27th, 

 1880. 



A few medical men interested in micros- 

 copy, brought their microscopes, and ex- 

 hibited histological objects, which were 

 changed every session. Most of the 

 members were interested in the matter. 



At the close of the morning session of 

 the second day, a microscopical section 

 was formed by electing Prof. J. J. M. 

 Angear, M. D., as President, and Prof. 

 W. D. Middleton, M. D., as Secretary. 



— The wax-cell which Dr. Hamlin des- 

 cribes in his article is really a good cell. 

 It may be thought that wax alone is too 

 soft for durable mounts, but this is not 

 the case. Experience has shown that it is 

 an excellent material for the purpose. Dr. 

 Hamlin has kindly send us a cell prepared 

 according to the instructions he has given, 

 and it is very neat and clean. We advise 

 our readers to give the process a fair 

 trial. 



— The prices of microscopes and acces- 

 sories seem to be going up. We notice 

 several changes in Beck's catalogue. 



QUESTIONS AND ANSWERS. 



[This column is freely open to all who desire in- 

 formation upon any subject connected with micros- 

 copy. It is hoped that the readers will reply promptly 

 to the questions which are asked.] 



answers. 



(I.) In the M. M.J., vol. 4, p. 18 (July 

 1870), Mr. Wenham refers to a photo- 

 graph of Angulatum " magnified fifteen 

 thousand diameters," exhibited previously 

 to 1854: One of the photographs is still 

 in the possession of Mr. Jabez Hogg. On 

 p. 124, Mr. Wenham refers to "eleven 

 thousand diameters," and on p. 125 gives 

 au outline-sketch with camera-lucida of 

 Podura with " six thousand diameters." 



The Rev. W. H. Dallinger has repeat- 

 edly mentioned " ten thousand diameters " 

 in his papers, and implies even higher 

 magnifications as being at his command. 



Messrs. Powell and Lealand have pub- 

 licly exhibited Angtilatum with " four 

 thousand diameters." 



Dr. Woodward's photographs go to 

 about four thousand diameters with great 

 success on certain boldly-marked objects, 

 but with Nobert's higher bands he ap- 

 pears to have obtained the best direct re- 

 sults with hardly more than one thousand 

 diameters. J. M., jr. 



London, Feb. 11, 1880. 



(3) If A. L. W. understands all the differ- 

 ent methods of constructing objectives, his 

 question can be intelligently answered. 



One method of constructing the front- 

 lens of high-power objectives — the one 

 in most common use by first-class makers 

 — is to make the front achromatic by com- 

 bining two or three lenses ; such fronts 

 are known as compound-fronts. Some 

 years ago Mr. Wenham, of London, intro- 

 duced fronts of a single lens. About 1872 

 Mr. Tolles added another single lens in 



