VI. MISCELLANEOUS--A Group of Hampshire Downs--A typical breed of sheep, their qualities and habits.--1 illustration. 9957 VII. NAVAL ENGINEERING--The Spanish Cruiser Reina Regente--A further description of this celebrated vessel--4 illustrations. 9948 Torpedo Boats for Spain--The Azor and Halcon, two Yarrow torpedo boats, described and illustrated--7 illustrations. 9947 VIII. PHOTOGRAPHY--How Different Tones in Gelatino-chloride Prints may be Varied by Developers.--Twenty different formulae for the above purpose. 9949 Film Negatives--Eastman stripping films, their manipulation and development. 9949 IX. SANITATION--French Disinfecting Apparatus--A portable apparatus for disinfecting clothes and similar objects--1 illustration. 9952 X. TECHNOLOGY.--The Manufacture of Cocaine--The extraction of cocaine with alkali and petroleum, with statement of percentage yielded by various leaves. 9954 The Production of Oxygen by Brin's Process--The commercial manufacture of oxygen by means of baryta--3 illustrations. 9950 #Transcriber's Note: Following entry not in original table of contents# Deep Sea Dredgings: Examination Of Sea Bottoms. By THOMAS 9958 T.P. BRUCE WARREN. * * * * * BENIER'S HOT AIR ENGINE. The hot air engine, although theoretically recognized for some time past as the most economical means of converting heat into motive power, has up to the present met with little success. This is due to the fact that the arrangement of the motors of this class that have hitherto been constructed has been such as to render them but slightly practical. In the Benier hot air engine (illustrated herewith), however, obstacles that were once considered insurmountable have been overcome, and the motor presents many advantages over all the types that have preceded it. Among such advantages we shall cite the possibility of utilizing air at a high temperature (1,200 or 1,500 degrees), while the rubbing surfaces remain at a moderate temperature (60 or 80 degrees). The fire grate is placed in the interior of the cylinder, and is traversed by the cold air forced by a pump. The expanded hot gases fill the cylinder and act against the piston directly above the grate.