L. MECHANICS AND ENGINEERING. 469 



* 



wheels, are drawn over the track. As this constitutes prac- 

 tically one rolling body, a comparatively small engine is suf- 

 ficient to convey the train. The invention has been made, 

 with special reference to the interest of India, for carrying 

 goods, coal, and even water over long distances, through a 

 thinly populated country at the least possible expense. They 

 are protected from the danger of fire and water, and involve 

 a minimum of dead weight. 3 A, September 26, 1874, 393. 



IMPROVEMENTS IN MINERS' SAFETY -LAMPS. 



In speaking of sounding and sensitive flames, Mr. A. S. 

 Herschel states that in the application of them to the con- 

 struction of miners' safety-lamps, which shall make an audi- 

 ble noise on the approach of dangerous gases, we must avoid 

 any vibrations except the extremely small oscillations of a 

 high-pitched note, otherwise elements of danger may be ap- 

 prehended from the sounding action of the flame. Accord- 

 ing to Dr. Irvine, the state of musical sensitiveness in Barry's 

 wire gauze sensitive flame is due to the increased inflamma- 

 bility of the burning gas mixture. The gas current, before 

 reaching the wire gauze, will naturally entangle and mix 

 with it a larger quantity of air when it is disturbed than 

 when it issues smoothly. Such a disturbance is produced by 

 the action of external sounds, under whose influence the ap- 

 pearance of the flame is more contracted and boisterous than 

 when the gas jet burns in a surrounding atmosphere of quies- 

 cent air. 12 A, XL, 1874, 88. 



IMPROVED CLOCK-WORK GOVERNOR. 



In order to secure perfectly regular motion in the clock- 

 work applied to revolving lights in light-houses, Dr. Hopkin- 

 son, the scientific adviser of the glass-works of Messrs. Chance 

 & Co., near Birmingham, states that he has introduced a 

 simple centrifugal governor. The governor balls have to 

 lift a heavy weight, which is in the form of a fly-wheel, the 

 circumference of which, on being raised slightly, presses 

 against certain fixed pads, the friction of which soon dimin- 

 ishes the velocity of rotation of the fly-wheel and the gov- 

 ernors, sufficiently to allow these latter to fall back to their 

 original position. He calculates that work to the extent of 

 five hundred pounds per minute must be done on the gov- 



