Eafy Method of LtvcU'tng, ' 467 



tahied by the operation of levelling, and not by computation as In our former fuppofition. 

 This operation is eafy, and may be performed upon fuch fliort diftances with fufficient ac- 

 curacy, with a carpenter's fquare and a ftafF. 



For this purpofe it will be neceffary to drive a pin into the handle, or thickeft part of- 

 the fquare, near the corner, upon the flat fide. A line muft be drawn from the pin, pa- 

 rallel to the edge of this handle, and a looped thread fupporting a fmall weight muft be 

 hung upon the pin. In this fituation the inilrua.ent is ready for taking levels. For if it 

 be held in fuch a pofition that the plumb line may cover the line drawn from the pin, the 

 blade will lie horizontal, and by looking along its upper edge the eye will be direclcd to 

 fome objeft on the fame level with itfclf. Let the obferver provide himfelf with a (lafF 

 five or fix feet long ; which, if divided into feet and inches, will be the more ufeful. 

 This is to be pitched at or near the lower end of the ftream,' and againft it the obferver 

 is to prefs the handle of his fquare, which may be conveniently done by grafping both 

 it and the ftafF together in the fame hand. Then, holding the apparatus fo that the plumb 

 line may lie fair, he is to direiS the blade of the fquare to fome ftone or other remarkable 

 obje£l; higher up the ftream ; for which purpofe it will be neceflary to Aide the handle of 

 the fquare up or down the ftafF till the pofitions are accurately obtained ; that is to fay, 

 till the blade points fairly to the obje£l at the fame time that the plumb line denotes that" 

 the blade is level. When this is done, a memorandum muft be taken of the feet and- 

 inches from the bottom of the ftaff to the upper edge of the blade, and the obferver muft 

 proceed to the ftone or objefl to which his fight was dire£led, and, planting his ftaflF there, 

 repeat the fame operation with regard to fome other objecl ftill higher up the ftream, and 

 again note down the feet and inches obferved upon the fl;afF. This procefs continued 

 will, by a few reiterations, bring him to the upper extreme of the water which we fup- 

 pofe to be within his grounds or power. The fum of all the meafures taken upon the ftafF 

 is the difference of level or whole fall of the water. The quantity of water in cubic feet 

 may be afcertained by either of the means before mentioned ; or, if the ftream be very 

 fmall, it may aflually be dammed, and meafured off" with two tubs or meafures, of as 

 large a fize as can conveniently be managed. 



I fhould be inclined to apologize to fuch of my readers as- are intimately acquainted 

 with thefe fubjefts, for the minutenefs of detail into which I have entered, if I were not 

 alFured that they will be the firft to perceive,, that many individuals who pofFefs beneficiat 

 ftreams are totally uninformed of their value, or of the means of determining the fame. 



(To be continued.) 



IX. 



Enquirits c.oncer.ning ihe Tnvention and Praclice of the Art of Hat making. 



To Mr. NICHOLSON. 

 SIR, Nevvcaftle, 15th Dec. 1798.. 



OUR Publication being open to enquiries relative to the advancement of manufac- 

 tures, as well as the fcienees, will you favour me with a place for the following queries,. 



