MECHANICS AND USEFUL ARTS. 77 



chanical force due to its quantity and volume is furnished through a 

 similar pump, which takes from the cistern a portion of the liquid, 

 and, after injecting it into the expanding air in the engine, returns it 

 to the same cistern. This cistern thus operates as a reservoir of cold, 

 and as the sufficient means of abstracting heat from water, which is 

 to be converted into ice. It is proposed to use the same air over and 

 over again, and thus the inventor attains the object of employing 

 air which previous condensation has deprived of heat, and subsequent 

 expansion has left at a lower temperature than the atmosphere. The 

 present imperfect machine has lowered a large quantity of matter 

 from 90 Fahrenheit to 5 below zero, and maintained it at the latter 

 temperature for a long time, with but little cost of power ; but a new 

 machine is now building, which it is supposed will succeed still bet- 

 ter, as some defects, natural to a new and original contrivance, have 

 been obviated in this second one. Ice can, it is expected, be made by 

 this process at a cheaper rate than it could be imported from the North- 

 ern States. 



GUTTA-PERCHA TUBIXG. 



A SERIES of interesting experiments has just been concluded at 

 the Birmingham Water-works, relative to the strength of gutta percha 

 tubing, with a view to its applicability for the conveyance of water. 

 The experiments were made upon tubes of three quarters of an inch 

 in diameter, and one eighth thick, of gutta-percha. These were at- 

 tached to the iron main and subjected for two months to a pressure 

 of 200 feet head of water, without being in the slightest degree de- 

 teriorated. In order to ascertain, if possible, the maximum strength 

 of the tubes, they w r ere connected with the Water Company's hy- 

 draulic prooling-pump, the regular load of which is 250lbs. on the 

 square inch. At this point they were unaffected, and the pump was 

 worked up to 337lbs., but, to the astonishment of every one, the tubes 

 still renmined perfect. It was then proposed to work the pump up to 

 SOOlbs., but it was found that the lever of the valve would bear no 

 more weight. The utmost power of the hydraulic pump could not 

 burst the tubes. The gutta-percha, being slightly elastic, allowed 

 the tubes to become a little expanded by the extraordinary pressure 

 which was applied, but on its withdrawal they resumed their former 

 size. Athen&um, August, 



CORDAGE-MACHINE. 



THE XPW Bedford Cordage Company have in operation a machine 

 for manufacturing ' ; shrouds " for ships, which effects a great saving 

 in time and labor over the old mode. By it, a length of shrouding 90 

 fathoms long, consisting of four strands, and weighing a ton, can be 

 completed and reeled in 33 minutes, requiring only the labor of two 

 men and two boys, whereas, but a few years since, it would have 

 taken thirty men half a day. It is claimed that superior strength and 

 durability are also gained by this process, as in "laying" the 



