122 ANNUAL OF SCIENTIFIC DISCOVERY. 



a series of friction rolls attached to the throttle valve, check or 

 increase the motion of the engine, the stem of the shaft of the pro- 

 peller-wheel passing through friction-rolls without packing, caus- 

 ing instantaneous and sensitive motion to depress or elevate the 

 throttle-valve. The governor is operated from the main shaft by 

 means of a belt and pulleys. 



A novelty in the display of minor tools is Jones' Patent Joint 

 and Mitre Planer, a hand-tool whereby a perfect right-angled or 

 mitre joint may be made, or a piece be planed square or to any 

 required angle, with ease and accuracy, even by the inexpert. 

 This is accomplished by an adjustable table, upon which the 

 piece is laid, and brought up to the cutting-iron of the plane, at 

 the angle desired. The plane proper runs on ways, and thus has 

 a perfectly parallel motion. Scientific American. 



GREEN GLASS FOR THE DARK ROOM OF PHOTOGRAPHERS. 



Mr. Gaffielcl, of Boston, has shown that while chemical rays to 

 a slight degree will pass through j^ellow glass, they are perfectly 

 excluded by green and red. This has suggested to photogra- 

 phers to substitute green glass for thej T ellow in the developing and 

 fixing room. The yellow light is very trying to the eyes, while 

 the green light is very agreeable. 



Carey Lea recommends the green glass, after an experience in 

 the preparation of hundreds of plates where it had been substi- 

 tuted for the yellow panes. 



A NEW WINDOW. 



The New York "Technologist 1 ' describes a new contrivance for 

 preventing people looking into a room, while light is not ex- 

 eluded. It consists of a number of glass rods arranged either 

 vertically or horizontally, and secured together by appropriate 

 frames, forming a series of cylindrical lenses which break up the 

 light and throw it into every part of the room, thus producing a 

 soft and diffused glow which is very beautiful and pleasant. The 

 glass rods may be of any color, and by an arrangement of the 

 colors very beautiful effects can be produced. The contrivance is 

 the invention of Mr. Deniuth. 



NEW DYE. 



The "Engineer" states that the new dye known as soluble 

 garnet seems to be coming more largely into use on the Continent, 

 and as the colors produced with it are exceedingly brilliant, simi- 

 lar to those obtained with archil, but much more stable when ex- 

 posed to light and air, the garnet dye is likely to become a great 

 favorite. The dye was first prepared by Casthelaz, of Paris, and 

 is the ammonia salt of isopurpuric acid, which is formed by the 

 action of a metallic cyanide upon picric acid. It is not prepared 



