16S THE AMERICAN MONTHLY [July. 



part advances a theory of transcendental dynamics, which, in the last 

 part, is applied to the creation of the universe. The author defines 

 force and energy as the two manifestations of power ; the first, tending 

 to initiate aggregative motion, finding its expression in gravitation, ad- 

 hesion, chemical affinity, and imperfectly comprehended electrical 

 affinity, and the second showing its vitality in the separative powers 

 classified as molar, molecular, chemical, and electrical modes or mani- 

 festations of motion. The illustrations of the operations of these antag- 

 onistic powers in aggregating the universe into more or less solid globes 

 on the one hand, and in hurling these globes through their orbits on the 

 other, are very instructive ; but it is not suggestive of comfort for some 

 far distant posterity to know that Mr. Grant Allen believes that the ag- 

 gregating forces are continually proving too strong for the separative 

 energies, and that the satellites are being continually drawn into the 

 planets, the planets into the suns, and the suns themselves into some 

 invisible and unknown centre of the universe. 



Practical Microscopy. By Geo. E. Davis. London, 1889. 8°, pp. 

 436, 310 figures, 1 plate. 



This is a revised edition of the author's earlier work, and seeks to 

 furnish full information about the instrument, its use, mounting, etc. 

 The colored frontispiece shows double-stained sections of several kinds 

 of wood — clematis, dog rose, eucalyptus, gout weed, black pepper. 

 Virginia Summer Resorts on the Norfolk & Western R.R. Pub- 

 lished by the Company. 12 , pp. 44. 



This very neat pamphlet describes and illustrates a large number 

 of resorts. It is apparently for free distribution upon application to 

 W. B. Bevill, General Passenger Agent, Norfolk, Va. Visitors to the 

 Blue Ridere will find it useful. 



SUBSCRIBERS' NOTICES. 



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

 FOR EXCHANGE.— Slides of selected diatoms. D. B. WARD, Poughkeepsie, 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 

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



OFFERED. — Diatomaceous Earth from Utah (Desert) for Histological Mounts. 



PROF. ORSON HOWARD, Salt Lake City, Utah. 



CORRESPONDENCE invited with a view to the exchange of either mounted or unmounted Oribatida 

 (British) for American species. E. BOSTOCK, Stone, Staffordshire. 



WANTED. — Specimens of rocks for slicing and grinding into sections ; also bones and teeth of differ- 

 ent animals, diatoms in situ on algae, diatomaceous and polycystinous earths, ocean soundings, etc., etc. 

 Liberal exchange in microscopic slides or cash. 



ARTHUR J. DOHERTY, 63 Burlington St., Manchester, Eng. 



TO EXCHANGE. — Native gold, silver, copper, lead, zinc, and other beautiful cabinet specimens, 

 polished ornaments and sections of petrified wood — Chalcedony — and native turquoise, agate, amethyst, 

 rubies, etc.; also Indian ornaments, curios, arrows, blankets, pottery, etc.; pelts of wild animals, species 

 of native cactus, and a good second-hand " Burt's Solar Compass" complete. Any or all of the above 

 are offered in exchange for new, or good second-hand, objectives, condensers, polarizers, stand, or other 

 microscopical apparatus. W. N. SHERMAN, M. D., Kingman, Arizona. 



OFFERED. — Zeiss' New Catalogue (in German) forwarded for 10 cents in stamps. 



F. J. EMMERICH & SONS, 43 Barclay St., New York City. 



WANTED. — Any works on Microscopy not already in my Library. 



H. M. WHELPLEY, F. R. M. S., St. Louis, Mo. 



WANTED. — (In exchange for slides.) "Microscopical Bulletin," Vol. I. No. 5, August, 1884, and 

 Vol. II, No. 1, February, 1885. M. S. WIARD, New Britai , Conn. 



