42 KANSAS CITY REVIEW OF SCIENCE. 



hour; how to put in movement a determined number of clocks by means of an 

 apparatus, at once normal and unique. M. Mayerhofer, of Vienna, a machine 

 manufacturer, has met the difficulty. By means of his pneumatique clock, he 

 is able, with compressed air, to lay on the exact hour, as water and gas are dis- 

 tributed by subterranean pipes, and since a year the street clocks of Vienna are 

 thus worked. The hands on the clocks correspond with the meridian of Vienna, 

 of course, and are connected with the central clock by means of tubing and com- 

 pressed air, which put in motion the minute and the hour wheels. The impulsion 

 comes from the central clock, itself in relation with the observatory. A piston works 

 in a cylinder filled with mercury and pushed by compressed air • a rectilineal 

 movement ensues, corresponding to minutes and hours which is transmitted by 

 the tubing to the several dials. In the central establishment are two reservoirs 

 of compressed air ; the first has a pressure of from two to four atmospheres, and 

 the second has one-half atmosphere only. In order that the latter may not vary, 

 the air is freed from its watery vapor by being passed over lime ; it is also regu- 

 lated that it will never exceed the pressure of one-half of an atmosphere. It is, 

 from this second or motive reservoir, that air passes into the tubes ; the orifice, 

 or escapement, closes at a fixed number of seconds, and the air rushing along 

 the tubes puts all the clock hands in motion, as it is being sucked back into reser- 

 voir number one. There is a tell-tale electric wire, like the service-telegraph in 

 a hotel, that indicates if any clocks be out of order. The invention is accuracy 

 itself and will be seen at work pending the exhibition. It is also so cheap that 

 the fronts of houses are being decorated with fancy clock dials. 



Glass type is making way, since Messrs. Montcarmont and Dumas prepare 

 it extensively, following the process of toughening the glass, as discovered by 

 M. de la Bastie. The letters in glass look as sharp and clear as those obtained 

 from the ordinary alloy of lead and antimony ; can be cast in the same mold 

 and turn out as well into the bargain. It cannot be "battered," and a blow 

 from a hammer will not injure it. Neither is any change experienced when the 

 forms are heated and then wetted to be suddenly cooled for stereotyping. A 

 pound of glass will yield five times more type than a pound of lead, and in addi- 

 tion, never wears. In chromo-printing, those colors having a base of copper, 

 cannot be employed with ordinary lead type ; the latter would decompose the 

 color. No such result ensues with glass type. Also it is cleaner. 



F. C. 



