TOI.. XI.] PHILOSOPHICAL TRANSACTIONS. 311 



the juncture of the two boards, nailing one end, by means of two small holes 

 bb, to the board A only, leaving the other end, which is the toothed one, free, 

 and reaching to a competent distance over the board B, to which it had no co- 

 herence. Next I made a pinion e, consisting of as many teeth as the piece of 

 brass had, on the end of a piece of thick iron wire: the axis F, with its pinion e, 

 I so fastened to the other board B, by means of the small arm E, and so adapt- 

 ed to the teeth of the brass plate, that when the boards shrink asunder, the 

 brass being drawn a little away, must needs turn this axis, by means of its 

 toothed pinion e, more or less; and thus, if ever it happens that the boards 

 gape but a quarter of an inch asunder, this axis will have made one entire revo- 

 lution : wherefore putting a long index GG on the extremity of this axis, and 

 making a circle round it with the usual graduations, numbered from any point 

 at pleasure, the motion of the index backward or forward, shows the degrees of 

 the drought or moisture of the air. Now this axis may be made to pass through a 

 round plate of wood or metal, that hides the contrivance, all but the hand and 

 figures, as in a clock or watch. It is to be noted, that the boards must be 

 fastened to the ledges, only at the outer edges, as at aaaa, that they may have 

 the more liberty of swelling and shrinking asunder. The commodiousness of 

 this kind of hygroscope in comparison of those made of wild oat-beards, may 

 best be observed by those that may try them both. 



I have here also sent you the figure of an admirable instance of nature's 

 luxuriancy, in her contrivance even of insects. Fig. 7^ ph 9> is a kind of large 

 flying beetle, of a dark shining brown, with a huge pair of horns, in propor- 

 tion to the body, shaped and branched exactly like a stag's or hart's, from which 

 last it is denominated, in Virginia and New-England, the flying hart. It is of 

 the shape and size of the figures above referred to. It flies high and swift, and 

 rests most commonly on branches or trunks of standing trees ; where, as eoon as 

 it has taken up its station, it begins with a shrill chirping voice, which it raises 

 by little and little till it makes the whole woods ring again; and then lessens 

 gradually, till it ceases with a kind of silent murmur, as if the little creature had 

 rung itself asleep : then it flies to some other place, and begins the same tune 

 again. The horns are of a shining hard substance, and the tips of them touch 

 the same plane with the belly. 



Though the author in N° 27, of your Transactions, seems inclinable to be- 

 lieve, that it is peculiar to the Thames water alone, upon stinking, to be re- 

 coverable or potable again ; I can aflirm upon my own knowledge, that water 

 taken aboard at New London in New-England, though in eight days time it 

 stunk intolerably, yet when we came to Virginia, it recovered so perfectly, that 

 I made no scruple to drink of it in harbour, even when we had fresh water 



