ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 515 



Dr, E. H. Ward, of Troy, N.Y., writes upon the subject as 

 follows : * — 



" In speaking of the modern microscopic rulings on glass, which 

 have been regarded with so great and deserved an interest by all 

 physicists, one cannot be too careful to discriminate fully between 

 those that are known to be ruled and those whose ruling has been 

 attempted but not yet demonstrated. It is self-evident that, in 

 attempting to rule lines 5,000,000 to the inch, a band may be pro- 

 duced which does not consist of lines of that degree of fineness. 

 There is no difficulty in arranging a machine to draw lines, theoreti- 

 cally, of any required degree of closeness. The register of a ruling 

 engine can be so arranged and subdivided as to indicate a spacing at 

 the ruling point of one ten-millionth of an inch as easily almost as 

 of one-tenth of an inch ; but it may well be doubted whether such 

 fine motion is actually imparted to the diamond point, or could be 

 recorded upon the surface of the glass. It is becoming common to 

 hear the higher bands of Mr. Fasoldt, claiming u]3 to 10,000,000 

 lines to the inch, spoken of as actually ruled, and only waiting an 

 objective to reveal them. Such an error, made inadvertently by 

 persons who would avoid it by a little reflection, as made in the last 

 number of one of the most popular microscopical journals, gives 

 a lasting as well as erroneous impression to non-scientific persons. 

 Mr. Fasoldt's rulings are certainly remarkable, and the lower bands 

 are ruled with great success ; but how far up the scale they continue 

 to be ruled as distinct lines is certainly at this time an undecided 

 question." 



Journal for Physical and Biological Instruments. — The ' Zeit- 

 schrift fiir Instrumentenkunde, Organ fiir Mittheilungen aus dem 

 gesammten Gebiete der wissenschaftlichen Technik ' f is a new journal, 

 of large octavo size, devoted to instruments used in physical and 

 biological science. The list of editors is headed by Professor E. Abbe, 

 of Jena, the editor in chief being Dr. Georg Schwirkus. The journal 

 occupies a new and important field, and will be of value to micro- 

 scopists, as it contains a number of articles on microscopical and 

 accessory instruments. Amongst the articles which have already 

 appeared may be mentioned two on the construction and examination 

 of micrometer screws, and on the illumination of micrometrical 

 apparatus in Telescopes and Microscopes. 



^ew Microscopical Journal. — A new illustrated bi-monthly 

 Journal has appeared at Detroit, U.S.A., under the title of ' The 

 Microscope and its Eelation to Medicine and Pharmacy.' It is edited 

 by Charles H. Stowell, M.D., Assistant Professor of Physiology and 

 Histology, and Louisa K. Stowell, M.S., Assistant in Microscopical 

 Botany in the University of Michigan. 



The first number consists of thirty-two pages, with seven wood- 

 cuts, and contains amongst others the following articles : — " Ipecacu- 

 anha, its Structure and Adulterations ; " " Membranous Dysmenorrhoea, 



♦ Amer. Natural., xv. (1881) p. 259. t 8vo.. Berlin, 1881. 



