1883.] 



MICROSCOPICAL JOURNAL. 



35 



the Journal will be regularly issued 

 on the 15th day of every month, and 

 if any change whatever is noticeable 

 in the Journal we trust it will be 

 such as will commend itself to all 

 readers. 



Change of Management. — Last 

 month we announced that the busi- 

 ness management of the Journal had 

 been transferred to Messrs. S. E. 

 Cassino & Co. As there seems to be 

 some misunderstanding about it, we 

 wish to add that Messrs. S. E. Cas- 

 sino & Co. are the publishers of the 

 Journal for the year 1883, that they 

 will fulfil all contracts for advertising 

 previously made by the editor. The 

 editor has relinquished the business 

 management of the Journal, and 

 placed it entirely in the hands of 

 Messrs. Cassino & Co., who are 

 authorized to collect payments for 

 advertisements and subscriptions for 

 the current vear. 



Remarks on Dr. Carpenter's Ad- 

 dress. — The report of Dr. W. B. Car- 

 penter's address at Montreal last sum- 

 mer, which was published solely in 

 this Journal, has been reprinted and 

 circulated in England by a member of 

 the Manchester Microscopical Society, 

 and is reviewed at considerable length 

 in the January number of the Micro- 

 scopical News. On the whole, the ed- 

 itor of that paper regards the views 

 expressed by Dr. Carpenter as per- 

 fectly supported by theory and ex- 

 perience. In regard to the assertion 

 that a 2-inch objective should resolve 

 the Podura scale, the magnifying 

 power of the ocular required for this 

 purpose has been calculated, and it is 

 found that an eye-piece magnifying 

 125 to 200 diameters, such as an E or 

 F of Ross, would be required. Hence, 

 a good 2-inch must bear an E-eye- 

 piece at least. But a i-inch with a D- 

 eye-piece magnifies as much as a ^ 

 inch as ordinarily used, yet it is said 

 that the i-inch so used makes a very 

 bad quarter, while the 2-inch must 



bear a still higher ocular. Conse- 

 quently, while it is admitted that a i- 

 inch of very wide angle makes a very 

 bad I-inch, it does not follow that it 

 makes a bad :|-inch. 



Another point in reference to the 

 2-inch is the angular aperture it must 

 have to resolve the Podura scale. 

 This has been calculated from the 

 measurement of the distances between 

 the markings of two scales, which 

 were found to be respectively 20007 

 and 2T000 of an inch. To resolve these 

 the minimum angle must be 207 n. a., 

 or 24° in air. 



Then follows an interesting com- 

 parison of the prices of objectives of 

 different kinds, in which the writer 

 makes a distinction between " a good 

 set " of English objectives for ^10 or 

 ^12, and "a set of good" English 

 objectives at over ;^36. 



Standard Sizes for Oculars and 

 SuBSTAGES. — The great convenience 

 of uniformity in the size of oculars and 

 substages is so patent that any dis- 

 cussion of the subject is quite unnec- 

 essary. A committee of the Royal 

 Microscopical Society of London, re- 

 ported some time ago in favor of two 

 standard gauges for eye-pieces, the 

 larger being a size much used in 

 stands made in England, the smaller 

 conforming to the gauge of many con- 

 tinental stands. The sizes recom- 

 mended are respectively 1.35 and 0.92 

 of an inch, external diameter. The 

 larger size is designated as No. i 

 guage, the smaller as No. 2. It is to 

 be hoped that our American makers 

 will adopt the same sizes. 



The gauge recommended for sub- 

 stages is 1.5 of an inch, internal di- 

 ameter. 



Rotifer and Philodina. — In the 

 course of a conversation with Mr. Ba- 

 len a short time ago, he referred to 

 the resemblance between Rotifer and 

 Philodi?ia, and said that the latter was 

 such a common animal that it was 

 doubtless often taken for Rotifer vul- 



