Correspondence.

Progress, Volume VI, Issue 4, 1 February 1911, Page 550

Correspondence.

(To the Editor.) Auckland, January 1(». ■ Dear Sir, —As a subscriber to your valuable monthly, .1. am writing to ask you or one ot your subscribers to place me in communication with someone interested in aviation. I noticed some time ago that an instrument is needed to indicate to the aviator the angle at which his machine is inclined to the earth. During experiments connected with an invention (now protected) I came across a simple elucidation of the question, but have not time at the present to prosecute the —yours sincerely, ERNEST E. DRESSY. c/o Post Office, Do von port, A uck lan d. =s * * (To the Editor.) Dear Sir,l am getting water laid on to cattle troughs and 400 gallon tank on stand 12ft. high, the water being pumped by windmill from creek about live chains away, the whole elevation from creek to tank being about 60ft. I wanted the plumber to put the delivery pipe into bottom of tank so as to get the pressure from tank on to troughs and garden without a second line of pipes. He objects, on the ground that it was less work for the mill if the pipe was carried up into the top of the tank. I thought the pressure would be the same. Who was right? - J. W. RAMSDEN. Kumeroa, 18/1/11. Your plumber is right, though his reason is wrong. It would, as a matter of fact, take a little less work on the part of the mill to pump the water into the bottom of the tank than over'the top, the pressure being about 2(slbs. to square inch in the former case, to about 281bs. roughly in the latter, as the water has to be lifted 4 feet further to get over the top of the tank. As a matter of practice, no good plumber would attempt to economise in the piping to the extent you suggest. To begin with, if the vratei* -w/ere pump6(l in ns suggested., through , the bottom of the tank, it would not circulate freely. Unless the tank were emptied the water that was last pumped in would be first out, the top becoming stale. To prevent undue pressure on mill pump valves while mill is standing, a check valve should be placed some feet away from it.