870 SEC. 16. GEOLOGY AND MINING. 



external atmosphere ; the friction, or difference of density of the two atmo- 

 spheres, is indicated by the difference of level of the two columns of water. 

 Advantages claimed are especially the facility of observation and the 

 steadiness of the columns. 



3384. Model of a Ventilator (Guibal). 



Royal Saxon Mining Academy, Freiberg* 



3384a. Indicator for Mining Purposes for the preven- 

 tion of Explosions, and for demonstrating the presence of 

 choke-damp in disused pits or old shafts. 



Dr. F. Schopfleuthncr, Vienna. 



This is a kind of balance to be set up in coal mines. It announces 

 immediately any evolution of gas, enabling the miners to protect themselves 

 at once against this dangerous substance. The existence of the gas is sig- 

 nalled by an electric telegraph. A very light sphere of glass hangs from 

 the one end of the beam of a balance, and is supplied with pure air from 

 the downcast shaft in such a way that between the admission tube and the 

 sphere some air always escapes to prevent the gas from penetrating the 

 sphere. When, however, by the presence of fire-damp the atmosphere sur- 

 rounding the apparatus is specifically lighter than pure air, the sphere, in 

 consequence of its weight, will sink and make contact with the electrical 

 conductor of the signalling apparatus. By this means both the miners and 

 the men at the head of the mine receive early notice of the presence of gas 

 in the mine. When several instruments are employed an ordinary numbered 

 table is necessary. 



3384a. Drawing of Guibal Ventilator for Mines. 



David P ember ton Morison. 



Drawing of Patent self-contained Guibal Ventilator 

 for Mines, Ships, &c. David Pemberton Morison. 



3384b. Model of Cooke's Displacement Ventilator. 



John Cooke. 



This is a rotary engine, as distinguished from centrifugal exhausters or 

 blowers, and is particularly applicable to the ventilation of mines. 



The model exhibits how in place of having the drum cranks, levers, and 

 connecting rods the full length joining the centres of the arcs and drums to 

 their working axes respectively, their dimensions, weights, and speed of re- 

 ciprocation are reduced to a minimum, while at the same time the deflection 

 of the shutter is almost eliminated, by getting firm hold of it at each end, 

 as far down as is desirable. 



The principles involved are two : 



1. Maintaining the same relative proportions of the crank, lever, and con- 



necting rod ; and 



2. Adjusting the angle of the cranks and of the radius rods or intermediate 



shafts to harmonise with the oscillation of the shutter. 



3385. Mining Barometer. Elliott Brothers. 



3386. Mining Thermometer. Elliott Brothers, 



3386a. Davis's Mining and Surveying Aneroid Baro- 

 meter, reading altitudes to 1 foot. John Davis and Son. 



