▼oil. LXV.] PHILOSOPHICAL TRANSACTIONS. 66 { 



though Mr. Buffon has left that point undetermined. The above account 

 Mr. C. thinks settles the question, relative to martins. i >■ 



XXXI f^. Description and Use of a portable Wind Gage. By James Lind, 



M.D., Edinburgh* p. 353. 



This simple instrument consists of 1 glass tubes ab, cd, of 5 or 6 inches in 

 length, pi. 13, fig. 4. Their bores, which are so much the better always for 

 being equal, are each about -j-V of an inch in diameter. They are connected 

 together, like a siphon, by a small bent glass tube ab, the bore of which is -^V 

 of an inch in diameter. On the upper end of the leg ab there is a tube of 

 latten brass, which is kneed or bent perpendicularly outwards, and has its mouth 

 open towards f. On the other leg cd is a cover, with a round hole g in the upper 

 part of it, tV of an inch in diameter. This cover and the kneed tube are con- 

 nected together by a slip of brass cd, which not only gives strength to the whole 

 instrument, but also serves to hold the scale hi. The kneed tube and cover are 

 fixed on with hard cement or sealing wax. To the same tube is soldered a piece 

 of brass e, with a round hole in it, to receive the steel spindle kl, and at f there 

 is just such another piece of brass soldered to the brass hoop gh, which sur- 

 rounds both legs of the instrument. There is a small shoulder on the spindle at 

 f, on which the instrument rests, and a small nut at i, to prevent it from being 

 blown off the spindle by the wind. The whole instrument is easily turned round 

 on the spindle by the wind, so as always to present the mouth of the kneed tube 

 towards it. The end of the spindle has a screw on it ; by which it may be 

 screwed into the top of a post, or a stand made on purpose. It has also a hole 

 at L, to admit a small lever for screwing it into wood with more readiness and 

 facility. A thin plate of brass k is soldered to the kneed tube, about half an 

 inch above the round hole g, so as to prevent rain from falling into it. There 

 is likewise a crooked tube ab, fig. 5, to be put occasionally on the mouth of the 

 kneed tube f, in order to prevent rain from being blown into the mouth of the 

 wind gage, when it is left out all night, or exposed in the time of rain. 



The force or momentum of the wind may be ascertained by the assistance of 

 this instrument, by filling the tubes half full of water, and pushing the scale a 

 little up or down, till the of the scale, when the instrument is held up per- 

 pendicularly, be on a line with the surface of the water, in both legs of the 

 wind gage. The instrument being thus adjusted, hold it up perpendicularly, 

 and turning the mouth of the kneed tube towards the wind, observe how much 

 the water is depressed by it in the one leg, and how much it is raised in the 

 other. The sum of the two is the height of a column of water which the wind 

 is capable of sustaining at that time ; and every body that is opposed to that 



* Now of Windsor. 



