j^o New applkatian of the Syphon. 



In this arrangement the firfl: veflel will empty itfelf into the fecond, which will clofe the 

 cocks in the pipes oppofite A and W, before air is admitted into the veflel A W. The 

 third will be filled from the fecond, and the water in the veflel A W will be let out. 

 Again, the third will deliver its contents in the fourth or loweft, which will keep the cocks 

 in the fmall pipes oppofite A and W clofe, until after the third veflel is empty, has rifen 

 up, and the external air can no longer enter the veflel A W. The fourth being theo 

 emptied by its fyphon, the pipes between the vefl'el A W and fyphon S Y will open. 



The diampter of the fecond veffel fliould be fomething lefs than either that above or 

 below it. The fourth fliould be filled before the fecond is empty ; tlie third will defcend 

 tlie laft and rife the firft: the fecond and fourth will rife together immediately after the 

 third. If the fecond and fourth were to rife before the third, the fyphon would direftly 

 receive a quantity of external air, and its operations would ceafe. It will therefore require 

 much caution to manage the cocks and valves, if another veflTel, fimilar to A W, is to be 

 filled while this lafl; is emptied, and emptied while it is filled. 



The vefl!el A W fliould not be large, and in order to overcome the buoyance of the ex- 

 trafled air, it is adviceable to make the length of the defcending branch of the fyphon 

 exceed the length of the afeending one as much as circumftances will admit, and to let the 

 loweft part of it be made of a conical divergent form. The velocity of the ftream will 

 be thus encreafed j the veflel A W will be fooncr filled with water ; and the deprcflion of 

 the two columns will be lefs liable to happen from very flight imperfedtions of work- 

 manfliip. 



I am, SIR, 



Your humble fervant, 

 Dahon, Feb. 17, i8oi. WILLIAM CLOSE. 



IV. 



On the Power of penetrating into Space by Telefopes ; with a comparative Determination of 

 the Extent of that Power in natural Vijion, and in Telefcopes of various Sizes and Con- 

 Jlrudions; illuJlratedbyfckQ ObJ'ervalions. By Win I am Herscuel^ LL.D. F.R.S. 



(Continued from page 506, J 



Wi 



E may now proceed to determine the powers of the inftruments that have been ufed 

 in my aftronomical obfervations ; but, as this fubje£t will be befl: explained by a report of 

 the obfervations themfelves, I fliall k\ei\ a feries of them for that purpofe, and relate 

 them in the order which will be moft illufl;rating. 



4 Firft, 



