Meafurement of a Baje on Houiiflow-Heatli. ^^r^ 



ex3(£lly of the fame length, fubflituted in then- fl:ead, with 

 iemi-circular holes (as reprefented in the Plate by dotted lines 

 near the joint of the handle) to receive the fteel arrows, then 

 to be made ufe of in the manner already mentioned. 



This moft excellent chain feems not to have fuftcred any 

 perceptible extenlion from the ule that has hitherto been made 

 of it. It is fo accurately conftrucled, that when ftretched out 

 on the ground, as in common ufe, all the long plates lying 

 vertically or edge-wife, if a perfon, laying hold of either end 

 with both hai]ds, gives it a flip or jerk, the motion is, in a 

 few feconds, communicated to the other end, in a beautiful 

 vertical Terpentine line ; when the perfon, holding that handle, 

 receives a fudden (hock, by the weight of the cbain pulling 

 him forcibly. The chain weighs about eighteen pounds, and 

 when folded up is eafily contained in a deal box, about four- 

 teen inches long, eight inches broad, and the fame in depth. 



Deal Rods, Tab. XVIII. 



k. The bafes which have hitherto been meafured in different 

 countries, with the greateft appearance of care and exaftnefs, 

 have all, or for the moft part, been done with deal rods of one 

 kind or other, whofe lengths being originally afcertained by 

 means of fome metal ftandard, were, in the fubfequent appli- 

 cations of them, corrected by the fame ftandard. Having thus 

 had fo many precedents, ferving as examples to guide us in our 

 choice, it w^as natural enough that we fhould purine the fame 

 method in the meafurement to be executed on Hovmfiow- 

 Heath ; taking, however, all imaginable care, that our rods 

 ihould be made of the very befl materiafls that could be pro- 

 cured; 



