MECHANICS AND USEFUL ARTS. 83 



SOFTENING WATER. 



The two principal sources of impurity in water which render it 

 unfit for household purposes, are organic matters, and salts of 

 certain metals producing hardness, as found respectively in river 

 and spring, or pump water. 



Dr. Clarke, of Aberdeen, patented a process for rendering cer- 

 tain hard waters soft by the addition of lime ; the soluble carbon- 

 ate, of lime, being rendered insoluble, takes down also, in a kind 

 of network, the principal part of the organic matter in a state of 

 solution. By this process certain salts, rather beneficial, are not 

 abstracted ; for instance, sulphate of lime tends to harden water, 

 but as a preservative against the effects of lead it is invaluable. 

 If water of 16 degrees of hardness could be rendered of about 5 

 or 6 degrees, at a moderate cost, it would prove invaluable to 

 manufacturers, beside the economy in fuel and saving in plant, 

 wherever steam boilers are required ; it would save great labor 

 in culinary and laundry operations; it would also be a more 

 wholesome aliment, promoting digestion, and preventing the dis- 

 eases arising from the presence of lime. The latest apparatus 

 for this purpose consists of a galvanized iron cylinder, about a 

 foot in diameter, and 3 or 4 feet high, in which are chambers 

 wherein prepared lime is placed. It may be placed in any con- 

 venient locality, and requires no attention except to put a small 

 portion of the lime in it, about once in two or three weeks ; the 

 cost of working is said to be about one fartjiing for 2,000 gallons. 

 The water enters the cylinder at one point, and quits it at another, 

 after having passed through the deposit of lime, as soft as rain 

 water, as clear as spring water, and much purer than either 

 Mech. Mag., 1867. 



RESPIRATION IN DANGEROUS GASES. 



Many plans have been devised for enabling men to penetrate 

 dangerous gases, in mines and similar places, for the purpose of 

 working or of rescuing their comrades. 



The plan of Mr. T. Y. Hall, of England, was of a permanent 

 character. Safety pipes of proper material were to be laid down 

 in the floor of the main galleries of a mine, in the direction taken 

 by the air, from the top of the "downcast" shaft into the work- 

 ings, and back through the "return "to the "upcast" shaft, 

 these to be provided with boxes or joints at mtervals of about 40 

 or 50 yards. An air-tight dress or casing is put on, so secured, as 

 in that of a diver, that the man wearing it breathes only the en- 

 closed air. Flexible tubes from the dress can be connected with 

 the boxes on the safety pipes, and these tubes removed at will by 

 the miner ; having advanced the 40 or 50 yards, the length of the 

 flexible pipe, it is unscrewed and attached to the next joint, so 

 that he breathes pure air though passing through an atmosphere 

 that would soon be fatal if breathed. 



Galibert's apparatus, approved by the French Academy, is 

 more simple, and permits free locomotion. A reservoir of air is 



