I1YG 



HYM 



eel whip cord) five feet long, and having 

 a graduated scale fixed to an index, mov- 

 ing on a fulcrum. The length of the in- 

 dex, from the fulcrum to the point, should 

 be ten inches ; that of the lever, from 

 the fulcrum to the middle of the eye, to 

 which the cord is -fixed, two and a half." 

 He adds, that "the principle on which 

 this hygrometer acts is obvious. The air 

 becoming moist, the cord imbibes its 

 moisture ; the line, in consequence, is 

 shortened, and the index rises. On the 

 contrary, the air becoming dry, the cord 

 discharges its moisture, lengthens, 

 and the index falls. It may be true," he 

 says, " that no two hygrometers will keep 

 pace with each other sufficiently to satis- 

 fy the curious. He will venture to say, 

 however, from seven months close atten- 

 tion, that two hygrometers, on this sim- 

 ple construction, have coincided suffi- 

 ciently for the uses of agriculture. It is 

 true," he adds, "they diminished in the 

 degree of action ; but as the scale may be 

 readily diminished in extent, and as a 

 fresh line may be so cheaply and so readi- 

 iy supplied, this is not a valid objec'ion." 

 It is remarked, that " this diminution in 

 the degree of action depends consider- 

 ably on the construction; the propriety, 

 or rather delicacy, of which rests, almost 

 solely, on this point : the weight of the 

 index should be so proportioned to the 

 weight of the lever and cord, that the 

 cord may be kept perfectly straight, with- 

 out being too much stretched. He made 

 one with a long heavy index, and in or- 

 der to gain a more extensive scale with 

 a short lever; but, even when it was first 

 put up, it could barely act; and in a few 

 weeks it flagged, and was not able to 

 raise the index, though the air was un- 

 commonly moist. He therefore made 

 another with the same length, both of in- 

 dex and lever, but with a lighter index, 

 and a heavier lever, so as to gain the pro- 

 portion above mentioned, and it has act- 

 ed exceedingly well." He thinks that 

 no farmer, " who wishes to profit by the 

 hygrometer, should have less than two. 

 Three or four would be more advisable. 

 They would then assist in correcting 

 each other; and, in case of renewal 

 or alteration, there would be no danger 

 of losing the state of the atmosphere ; 

 which, if only *one is kept, must neces- 

 sarily be the case. The principle on 

 which this hygrometer is formed is not, 

 he says, confined to a small cord, and an 

 index of ten inches long: it may be ex- 

 tended to a rope, of any length or thick- 

 ness, and to an index and scale of almost 

 any dimensions and extent." But one, or 



more, on a portable construction, might, 

 he thinks, be found useful. An axe is the 

 form he has thought of; the edge, gradu- 

 ated, will constitute the scale ; and the 

 handle will receive the cord : this may 

 be hung up in the shade, exposed to the 

 action of the air ; or, by means of a spike 

 in the end of the handle, it may be placed 

 in the open field. By placing it on fallow 

 ground, it may be actuated by the per- 

 spiration of the earth ; among vegetables 

 by vegetable perspiration ; by the means 

 of one, or, more probably, by the means 

 of several, placed at varied heights, the 

 different degrees of moisture at different 

 altitudes may be ascertained, &c. In fact, 

 he considers the hygrometer, whether it 

 is a prognostic of the weather or not, as a 

 most valuable oracle to the farmer. See 

 WEATHKR. 



HYMEN, in anatomy, a thin membrane 

 stretched transversely across the vagina, 

 at a small distance from its entrance. It 

 is sometimes found entire, completely in- 

 terceptingthe passage sometimesit ex- 

 ists but partially and often not at all. 



HYMENS, in botany, a genus of the 

 Decandria Monogynia class and order. 

 Natural order of Lomentaceae. JLegumi- 

 nosx, Jussieu. Essential character: calyx 

 five-parted ; petals five, almost equal ; 

 style twisted inwards ; legume filled with 

 farinaceous pulp. There is only one spe- 

 cies, viz. H. courbaril, locust tree. The 

 wild bees are fond of building their nests 

 in this tree, which grows to a considera- 

 ble size in the West Indies, and is looked 

 upon as excellent timber; but it must be 

 very old before it is cut, otherwise the 

 heart will be but small. It is in great re- 

 quest for wheel-work in the sugar mills, 

 particularly for cogs to the wheels, being 

 remarkably hard and tough. Professor 

 Jacquin says, that a cubic foot weighs 

 about a hundred pounds, and that it will 

 take a fine polish. 



HYMENOPTERA, in natural history, 

 the fifth order of insects according to the 

 Linnaean system. The insects of this or- 

 der are furnished with four membrana- 

 ceous wings, and also with a sting, or a 

 process resembling one. The wasp and 

 the bee are insects of this order. It con- 

 sists of the following genera: 



Ammophila 



Apis 



Chalcis 



Chrysis 



Cynips 



Formica 



Ichneumon 



Leucopsis 



Mutilla 



Scolia 



Sirex 



Sphex 



Tenthredo 



Thynnus 



Tiphia 



Vesna 



