84 ANNUAL OF SCIENTIFIC DISCOVERY. 



carried on the back, fixed by means of braces to a waist-belt; 

 the bag is made of a strong linen envelope externally, lined with 

 a finer one, each covered with numerous layers of India-rubber; 

 the usual capacity is 140 litres (1.76 to the pint), which will 

 allow a man to remain 35 minutes in the most deleterious gases 

 without inconvenience. From the bag tubes extend over the 

 shoulders, provided with properly secured nose and mouth pieces. 

 The man takes air from the reservoir* and respires into it again, 

 breathing the same air many times over without inconvenience. 

 When the respirations become frequent, he begins to prepare to 

 retreat, though after the first warning he can remain 7 or 8 min- 

 utes without danger. It can be prepared and adjusted in half a 

 minute, and requires no .instruction to use it, and will probably 

 save many lives of workmen overtaken by "choke damp, 1 ' or 

 carbonic acid. 



The apparatus of Mr. Rouquayrol, engineer to the Aveyron 

 collieries in France, consists of a reservoir made of thick iron 

 plates, capable of resisting a pressure of 25 to 40 atmospheres ; 

 the air is injected by very ingenious pumps, in which the pistons 

 are fixed and the cylinders move. When charged with air, it is 

 placed on the back like a knaj>sack ; a kind of mechanical bellows 

 is placed on the top, allowing the air, although at a very great 

 pressure, to enter the lungs at the ordinary pressure ; a little 

 exterior valve, of two leaves of India-rubber, held together by 

 the pressure of the atmosphere, opens itself to let out the respired 

 air. With this apparatus a man can breathe with the same ease 

 under water, and successful experiments have been made with it 

 at the bottom of rivers and of the sea, and in the sinkings of 

 mines; it is far preferable to the awkward and heavy dress 

 usually worn by divers. Air may also be supplied to a Davy 

 safet} 7 -lamp by this apparatus, ensuring a continuous light in 

 searching for disabled miners. Quart. Journ. of Science, April, 

 1867. 



IMPROVED TANNING PROCESSES, 



Mr. G. L. Loversidge, of England, has recently patented an 

 improved process for the preparation and dressing of hides and 

 skins for market. It consists in the employment of valonia and 

 oak bark, or other tanning materials, in conjunction with a solu- 

 tion either of caustic soda, carbonate of soda, ammonia, carbonate 

 of ammonia, or with mixtures of any of these solutions. A con- 

 siderable saving of time is thus effected, and a leather of superior 

 quality obtained. Mecli. Mag., Oct., 1867. 



Novelty in Tanning. A tannery has been located at Rockford, 

 111., in which is employed the patented process by exhausting the 

 air from the vat. The tanning is said to be accomplished in 

 12 hours, and that of sheep skin in 15 minutes. The weight of 

 leather from a given weight of hides is 10 per cent, greater than 

 by the ordinary process, and the cost of the works is but 10 per 

 cent, that of the old. 



