SUMMARY OF HYDRAULICS. 85 



The firft pump, invented above a century before Chrift, by The firft pump 

 Ctefibius of Alexandria, to whom alfo mufic is indebted for was a forcer 

 the organ, and whofe name Mr. Eytelwein mentions in fpeak- 

 ing of fucking pumps, was in reality a forcing pump, as may 

 eifily be collected from its description by Vitruvius (L. X. 

 cap. 12.) 



Chapter 18. Of mixed pumps, or the combination of fuck- Mixed pumps, 

 ing and forcing pumps. 



When the lower valve is above the furface of the water, the 

 forcing pump can only raife the water by faction, but the con- 

 struction remains the fame. Such is Mr. Buchanan's patent 

 fhip pump. De la Hire's pump is more complicated; both 

 die afcending and defcending ftrokes of the pifton being made 

 cfTective, by means of a double apparatus of valves and pipes. 



Chapter 19. Of a&ing columns of water. Included co- 



The mechanifm of a pump may be employed for convert- pre flure. 

 ing the weight of water defcending in its barrel, to the pur- 

 pofe of working another pump. The author defcribes a ma- 

 chine of this kind invented by Mr. Holl, and improved by 

 Langfdorf. A fimilar arrangement, ufed in Cornwall, has 

 lately been defcribed in Nicholfon's Journal, by Mr. Trevi- 

 thick. The only objection to it appears to be the magnitude 

 of the friction. 



Chapter 20. Of the fpiral pump. The fpiral pump 



Tf -J • j l- j e i • k *l • • or h O"zo nt al he- 



ir we wind a pipe round a cylinder, ot which the axis is ij x forcing water 



horizontal, and connect one end with a vertical tube, while U P a pipe* 

 the other is at liberty to turn round and receive water and air 

 in each revolution, the machine is called a fpiral pump. It was 

 invented about 1746, by Andrew Wirz, apewterer in Zurich, 

 and was employed at Florence with Bernoulli's improvement, 

 in 1779. At Arch an gel Iky, near Mofcow, a pump of this kind 

 was erected in 1784, which raifed a hoglhead of water in a mi- 

 nute, to a height of 74 feet, and through a pipe 760 feet in 

 length. The force employed is not mentioned, we may there- 

 fore conjecture that it was turned by water. Mr. Eytelwein 

 enters very minutely into calculations of the effect of fuch a 

 machine under different circum fiances ; and the refults of the- 

 ory, as well as of experiment, are fuch, as to induce us to ex- 

 pect that it will in time come into common ufe, inttead of 

 forcing pumps of a more complicated and expenfive conltruc- 

 tion.. The water-tight joint prefents the only difficulty: the 



pipe 



