474 Progress of Invention. 



as it may be wished to mark down only certain points of the pano- 

 rama, an arrangement is made which secures the attainment of this 

 object. Snould it be desired to observe not different pumts, bat 

 successive changes at the same point, the objective and the screen 

 are disconnected, so that only the latter revolves; the successive 

 appearances at the same point are then recorded in succession in a „ 

 circle round the sensit.zed plate. 



Compound Pipes. — To obviate the dangers which, especially in 

 certain circumstances, have been found to attend the use of leaden 

 pipes, and at the same time to secure the cheapness and other good 

 qualities of lead, a very simple mode of forming pipes, consisting 

 externally of lead, but internally of a thin shell of tin hrmly at- 

 tached to the had, has been invented. The cylinder of which the 

 pipe is to be lorined, by drawing, is externally of lead, but internally 

 of tin, both being hrmly united together, and the relative thick- 

 nesses of the metals being such, that when the lead is drawn to the 

 proper ieugi h, the coating of tin will be ol the desired depth. The 

 tin, which very slightly augments the cost of production, will remain 

 entire, however thin the pipe may be, if ordinary care is taken. 



Clearing of Ships from Bilge Water or Leakage. — A very 

 simple mode of effecting this is coining into use on the rivers of the 

 Western States of America. It is founded on the principle of 

 Giffard's injectors, and consists in placing in the vessel to be 

 emptied a pipe, in ordinary cases, about two inches in diameter, 

 with one extremity reaching to very nearly the bottom of the hold, 

 and the other projecting through its side a little above the water 

 line. Then insetting the conical extremity of a small pipe leading 

 from the steam boiler, and htted with a SLop-cock, into tne end next 

 the bottom of the vessel. If water reaches above the lower end of 

 the larger pipe, turning on steam into the smaller will cause the 

 water to be carried off with great velocity. It is not necessary that 

 the steam boiler should be in the vessel which is to be cleared of 

 water. The steam vessel may be alongside of the barge, etc., 

 which is to be emptied, and the larger pipe may be laid down 

 temporarily, the upper end being merely turned over the side : and 

 steam may be conveyed to the conical nozzle inserted in the lower 

 end of the larger pipe by means of a small flexible pipe leading from 

 the boiler ot uie steamer. 



Economic Production of Oxygen for Industrial Purposes. — 

 Oxygen is now obtained very economically by decomposition of 

 sulpnui ic uc.d. This is effected by means of heat, and an apparatus 

 devised for the purpose. The acid is decomposed into oxygen 

 and sulphurous acid, and the latter is removed by liquefaction, 

 effected by pressure. The sulphuric acid employed is not wasted, 

 it is merely the vehicle for obtaining oxygen from the atmosphere, 

 and may therefore be employed over and over again, the .sulphurous 

 acid being, alter each operation, changed back again into sulphuric 

 acid in tne usual way. A kilogramme of sulphuric acid at bU 5 

 affords a cubic metre of oxygen. 



Modification of the Pneumatic Despatch. — The Pneumatic 



patch, as organized at Paris, differs in some points, and ad van- 



