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contrived by him. He also invented a valve for equalizing the flow of 

 water, and thus ensuring the safety of persons using hydraulic lifts by a 

 proper regulation of the speed, irrespective of variation of the weight by 

 difference in the number of persons employing them. This valve is in 

 common use at all the large hotels. 



A very pretty contrivance was invented by him for throwing air into 

 water-pipes under great pressure. At the waterworks of the South Essex 

 Company water is pumped 12 miles and raised 400 feet by the direct action 

 of the engine. Under these circumstances the air in the air-vessel was ab- 

 sorbed by the water, and the use of an air-pump caused great heat from the 

 compression of the air. On consideration of all the facts, he immediately 

 contrived an injector, by which a suitable quantity of air was thrown into 

 the air-vessel without the aid of any pump. 



He also devised a simple method to avoid the bursting of water-pipes in 

 houses when the water is suddenly shut off at high pressures, and also to 

 prevent the unpleasant noise which occurs under these circumstances. His 

 contrivance consists in soldering a foot of pipe, closed at one end and full 

 of air, vertically near the tap. This acts as an air-vessel, and perfectly 

 prevents the noise or the risk of fracture of the pipe. 



The Appold overflow for cisterns is an ingenious application of scientific 

 principles, by which cisterns can be filled with safety to a very short 

 distance of their top. The overflow consists of a funnel-shaped pipe, con- 

 tracted at the bottom and very large at the top. This is covered with an 

 inverted metallic saucer, so that when the water flows fast the whole pipe 

 is filled, and vvith the covering constitutes a siphon which powerfully sucks 

 down the water. 



Mr. Appold also warmly advocated the use of siphons to carry water 

 over an embankment instead of having culverts through the bank. For 

 this purpose he recommended that one valve only should be used, and that 

 it should be placed at the upper part of the siphon, so that facility of exa- 

 mination m.ay be secured. Mr. Appold also suggested to Messrs. Easton 

 and Amos the arrangement of air-pumps which are employed for the ex- 

 haustion of the siphons at Kings Lynn. 



Great as Mr. Appold was in his knowledge of hydraulic principles and 

 in his application of them, he was no less fortunate in his successful appre- 

 ciation of pneumatic science. He was a thorough master of ventilation, 

 and that at a time when the principles of the art were but imperfectly 

 known ; his own house was for years regarded as a model of perfection 

 in that way, as fresh air of regulated temperature and moisture, and 

 thoroughly screened from all impurities, was abundantly supphed by a 

 scries of most ingenious self-acting contrivances. The Appold motor- 

 hygrometer which Mrs. Appold presented to the Royal Society, whereby 

 a self-acting motive power was obtained under any desired condition of 

 hygrometric moisture, is a very remarkable example of the skill with 



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