144 THE AMEEICAN MONTHLY. [June. 



The assistance of photography in the investigation of minute structure 

 is of great importance, as it reduces more nearly to a mathematical 

 plane the portion viewed. It also confirms the results obtained in the 

 resolution of difficult tests. With some experience one can finish four 

 or five negatives in an evening. Such expedition ought to satisfy the 

 most exacting. 



BOOK NOTICES. 



Catalogue of the Scientific Publishing Company. i6°, io8 pp. 27 

 Park Place, New York. 1S90. 



This is a very handy and classified catalogue of scientific and techni- 

 cal books for the use of those desiring to select works on the following 

 branches of science : Chemistry, assaying, engineering, physics, me- 

 chanics, metallurgy, and mining. An index of authors is also given. 



Catalogue., i8go. Ginn & Co. 



We are in receipt of the catalogue for the present year of this well- 

 known firm, which contains a full list of the late publications of that 

 house, together with the introduction prices.^ A careful perusal of its 

 pages will well repay those desirous of keeping abreast of the literature 

 of the day, and especially teachers, who will find much to interest them 

 in the outlines of new text-books. The catalogue will be sent on ap- 

 plication to all interested in literature. 



Heroic Ballads. Edited by D. H. Montgomery. 12°, 319 pp. Ginn 

 & Co., Boston. 1S90. (Price, 50c.) 



This volume is made up of a series of selected ballads, with careful 

 analyses and copious critical comments. As the book is intended prin- 

 cipally for school use, the selections are given in most cases without 

 abridgment, and where omissions do occur it is with the view of bet- 

 ter adapting the work to the school-room. The convenient foot-notes 

 on each page serve as an excellent exposition of the general ideas per- 

 vading the different ballads, a feature which should meet with popular 

 approval. The book is supplemented by an index to notes and also 

 by an index to authors. 



SUBSCRlBEliS' NOTICES. 



[These notices will be given six insertions in this cohimn at 25 cents per line or fraction thereof. 

 Ft)R EXCHANGE.— Slides of selected diatoms. D. B. WARD, Poiighkeepsie, N. Y. 



WANTED. — Unmounted microscopical material, also micrographic dictionary. Will exchange or 

 buy. CHARLES VON EIFF, 124 Clinton Place, New York City. 



WANTED.— A clean copy of Rev. William Smith's British Diatoms, and Schmidt's Atlas of the 

 Diatomacese. JAMES B. SHEARER, Bay City, Mich. 



OFFERED. — Diatomaceous F^arth from Utah (Desert) for Histological Mounts. 



PROF. ORSON HOWARD, Salt Lake City, Utah. 



CORRESPON DENCE invited with a view to the exchange of cither mounted or unmounted Oribatida 

 (British) for American species. ' E. BOSTOCK, Stone, Staflfordshire. 



