L ^o5 J • 



in water, &c. to that depth : this pipe, towards its upper end, is fo 

 narrow, as only to allow a fmall vibration of it on the point of 

 lufpenfion /<, without bringing its fides into contad: with the 

 qpright fpindle E E^ for thus it will prefent a lefs furface to 

 the impulfe of the wind ; but when it vibrates on the needle, 

 the loweft part only of. the pipe muft be allowed to ftrike againft 

 the rod EE^ left the point of the needle fhould be broken. The 

 weight is reprefented at P P ■■, it is a maflive ring of brafs 

 weighing about one pound and a half, foldered on the pipe CC, 

 (or it might be caft in the fame mafs with it) ; after which 

 the whole was carefully turned in a lathe, in order that its 

 fides might be equally thick all around; for thus they will 

 lie equidiflant from the rod E E, when this is in a vertical 

 pofition, and the inftrument hangs freely on the point of fufpen- 

 fion ; i. e. when the cafe MN \% fet on its bafe, and refts fteady 

 on the ground or fome level ftand, or is fo fupported, that it 

 remains ered, and in circumftances fit for making an obfer- 

 vation. To render it capable ot being carried about in its cafe 

 without injury, a brafs ring, having the form and indenture in it 

 reprefented at FF, is fattened within the cafe M N; which is 

 done by four fcrews paffed though its fides, that it, and alfo the 

 level, may be introduced and taken out ; and the upper part of the 

 weight PP has a fhoulder formed on it to fit and fill the in- 

 denture h in the ring, into which it is unerringly introduced by 

 the conical part of the weight above the fhoulder, when the weight 

 is pufhed up to it ; and this is done by advancing againft it the 

 fcrews D D, which move through the bottom plate of the cafe 

 Vol. VIII. O MN, 



