484 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



A METHOD OF RAISING AND LOWERING THE SCREW OF A 



PROPELLER. 



Mr. Harland, of Belfast, gave an account before the British 

 Association of his method for raising and lowering the screw 

 propeller in ships, remarking that during some voyages, and 

 especially across the Atlantic, the wave line of the side of the 

 ship was very often such as to leave an ordinary screw half 

 exposed. Under these circumstances the engine has only 

 half work to do, and consequently is apt to run off at such 

 speed as to injure the machinery. To prevent this he has 

 devised a simple method of lowering the screw, enabling the 

 engineer in heavy weather to keep the vessel going much 

 steadier, with very little reduced speed. A large amount of 

 power was thus utilized, with the advantage of a uniform 

 motion. In the normal position of the screw the tip should 

 be in a line with the keel; but when the vessel is in more 

 water than she really requires, the screw can be lowered, in- 

 volving no change in the speed of the engine. To prevent 

 the screw coming in contact with fishermen's nets, or other 

 obstacles, a small shoe can be slipped under it if necessary. 

 Mr. Harland's invention includes also a method of elevatinsr 

 the screw, to avoid contact with ice or other floating objects, 

 and to enable it to be repaired without the necessity of actu- 

 ally taking the vessel into dock. The operation of raising 

 and lowering the screw is readily and rapidly performed 

 by means of a small engine on the deck. 15 A, August 29, 

 1874,28V. 



PROPOSED CANAL THROUGH THE DESERT OF SARDAR ABAD. 



While the French are proposing to cut a canal from the 

 Gulf of Gabes, for the formation of an immense sea in Algeria 

 and Tunis, Mr. Hobham is about attempting to divert the 

 Avaters of the Arpatchai into a channel to be cut throughout 

 the length and breadth of the vast desert plain of Sardar 

 Abad for its thorough fertilization and cultivation. The 

 work has already been begun, under the grant of the plain 

 from the Russian government, and it will probably cost five 

 millions of roubles for its completion. Mr. Hobham hopes to 

 attract one hundred thousand Irish and German immigrants 

 to settle on the reclaimed lands. 13 A, Sept. 4, 1874, 263. 



