This is the celebrated article contributed by Andrew Ross to the “Penny Cyclopædia,” and quoted so frequently by writers on the Microscope. Carpenter and Hogg, in the last editions of their works on the Microscope, and Brooke, in his treatise on Natural Philosophy, all refer to this article as the best source for full and clear information in regard to the principles upon which the modern achromatic Microscope is constructed. It should be in the library of every person to whom the Microscope is more than a toy. It is written in simple language, free from abstruse technicalities. ------------------------------------------------------------------------ =Diatoms.= Practical Directions for Collecting, Preserving, Transporting, Preparing and Mounting Diatoms. By Prof. A. Mead Edwards, M. D., Prof. Christopher Johnston, M. D., Prof. Hamilton L. Smith, LL. D. 12mo., Cloth. 75 cents. This volume undoubtedly contains the most complete series of directions for Collecting, Preparing and Mounting Diatoms ever published. The directions given are the latest and best. ------------------------------------------------------------------------ =Common Objects for the Microscope.= By Rev. J. G. Wood. Upwards of four hundred illustrations, including twelve colored plates by Tuffen West. Illuminated Covers. 50 cents. This book contains a very complete description of the objects ordinarily met with, and as the plates are very good, and almost every object is figured, it is a most valuable assistant to the young microscopist. ------------------------------------------------------------------------ =Five Hundred and Seven Mechanical Movements.= Embracing all those which are Most Important in Dynamics, Hydraulics, Hydrostatics, Pneumatics, Steam Engines, Mill and Other Gearing, Presses, Horology and Miscellaneous Machinery; and including Many Movements never before published, and several of which have only recently come into use. By Henry T. Brown, editor of the “American Artisan.” Eleventh Edition. $1.00. This work is a perfect Cyclopædia of Mechanical Inventions, which are here reduced to first principles, and classified so as to be readily available. Every mechanic that hopes to be more workman, ought to have a copy. ------------------------------------------------------------------------ =The Six Days of Creation.= The Chemical History of the Six Days of Creation. By John Phin, C. E., editor of “The American Journal of Microscopy.” 12mo., Cloth. 75 cents. ------------------------------------------------------------------------ =Stories About Horses.= Just the Book for Boys. With eight full-page engravings. In Boards, 25 cents. In Cloth 50 cents. ------------------------------------------------------------------------ =Shooting on the Wing.=