MECHANICS AND USEFUL ARTS. 85 



CARRE'S ICE-PRODUCING MACHINE. 



The principle of this machine consists of sulphuric acid, mark- 

 ing 59 to 66, circulating in a thin stream, through which passes 

 vapor of water drawn along by a vacuum created pneumatically. 

 The evaporation of this produces the cold. The recipient of the 

 acid is formed of an alloy, of lead and antimony, in the proportion 

 of 5 to 6 per cent. ; it supports, without alteration of form, a pres- 

 sure of 5 or 6 atmospheres, while the pressure in practice cannot 

 exceed 1 atmosphere. The copper pump is preserved from the 

 contact of the sulphurous acid, always disengaged by the acid 

 recently introduced, by an arrangement which necessarily and 

 constantly oils the inside surface. The valves are opened mechani- 

 cally, and cannot get deranged. The apparatus keeps the vacuum 

 for several months ; the acid is extracted when it has become di- 

 luted to about 52 ; the congelation commences generally 3 or 4 

 minutes after the commencement of making the vacuum ; if cold 

 water at 3 or 4 C. is required, 2 minutes suffice, and a little shak- 

 ing up for some instants restores the air which it has lost. Other 

 substances can be substituted for sulphuric acid (which is, how- 

 ever, the cheapest agent to employ), such as caustic potash or soda, 

 or chloride of calcium, which cause a congelation sufficiently 

 prompt and intense. In the application M. Carre mentioned the 

 adaptation of the apparatus on board ships and in cellars where 

 the temperature could be indefinitely kept at 5 or 6 C. in all lat- 

 itudes, also for the refrigeration of apartments. 



M. Thenard first called attention to the curious and important 

 fact discovered by milk-women, and of which he cannot find an 

 explanation. If milk, a few minutes after being drawn from the 

 cow, be cooled with very cold rain-water, it keeps fresh for many 

 days, and can be sent to a long distance. Carre's apparatus can 

 advantageously replace the cold water, especially in agricultural 

 distilleries, which employ a good deal of sulphuric acid and keep 

 at the same time a great number of cows. Chemical News. 



ASPHALT PAVEMENT IN PARIS. 



Visitors to Paris are generally surprised at the appearance of 

 the pavement of a great number of streets in the central parts 

 of the town, and still more at the peculiar mode of making and 

 repairing this asphalt pavement if they chance to see those op- 

 erations carried out. The asphalt pavement was introduced into 

 Paris in 1854, by M. Momberg, chief engineer, and M. Vandrey, 

 engineer of the municipal service of the town of Paris. The first 

 street paved in this manner was the Rue Bergere. The asphalt 

 used for this purpose is a natural composition of pure carbonate 

 of lime and of bitumen or mineral tar. It is found in abundant 

 quantities at Seyssel, in France, and at Val-de-Travers, in the can- 

 ton Neuchatel, in Switzerland. In the first-named locality the 

 layers of bituminous limestone are from 4 to 7 yards deep, and of 

 very uniform composition, containing about 66 per cent, of bitu- 

 men and 34 per cent, of carbonate of lime. The natural stone is 



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