II VG 



HYP 



explains the mechanical properties of 

 fluids. 



HVDROSULPHURIC ACID. Sul- 

 phuretted hydrogen. See Sulphur. 

 Hydrosulphurets are the sulphurets 

 or sulphides of metals and bases. 



HYGEINE (from vyieia, health). 

 The arts necessary to the preserva- 

 tion of health. 



HYGROMETER (from vypoc, 

 moist, and fierpov, a measure). A con- 

 trivance or implement to measure 

 the amount of moisture or vapour of 

 water in air. Formerly hygrometric 

 substances, as hair, catgut, whale- 

 bone, sponge dipped in pearlash, &c., 

 were used ; but their indications are 

 of little value. The plan of ascer- 

 taining the dew point (see) is the sim- 

 plest ; this may be done as directed 

 under dew point, with the hygrome- 

 ter of Professor Daniel, or by a sim- 

 ple implement of Professor Bache, 

 which consists of a small bar of pol- 

 ished steel, in which several perfora- 

 tions are made, at short intervals, 

 large enough to receive the bulb of 

 a small thermometer. When used, 

 one end of the bar is plunged in iced 

 water, the other being sustained in 

 the air: after a short time, dew will 

 be seen to form near the lower parts, 

 and to rise gradually until it attains 

 a stationary point. If the thermom- 

 eter be now placed in the nearest ap- 

 erture, it will indicate the tempera- 

 ture of the dew point, or the hygromet- 

 ric condition of the air. If the place 

 occupied by the dew be situated be- 

 tween two perforations, the thermom- 

 eter may be placed in both, and one 

 half the difference added to the de- 

 gree of the lower, to mark the dew 

 point. 



The real amount of water in a giv- 

 en bulk of air is not measured by any 

 instrument. It is, however, a mat- 

 ter of calculation. From Professor 

 Daniel's table, it appears that at a 

 dew point of 30= Fahrenheit, there is 

 about 2i grains of water in a cubic 

 foot of air ; at 40°, 3i grains ; at 50°, 

 4^ grains; 60°=6i grains ; 70° Fah- 

 renheit = 8} grains ; at 80° Fahren- 

 heit, lU grains. 

 HYGROMETRIC, HYGROSCOP- 

 412 



IC. Having the quality of absorb- 

 ing moisture during wet, and partially 

 losing it in dry weather. 



HYGROSCOPE. The hygrometer. 



HYLOBIUS. A genus of tetram- 

 erous beetles, resembling the curcu- 

 lios, and infesting trees. 



HYMEx\IUM. The gills or porous 

 membranes in which the spores of 

 fungi are placed. 



HYMEXOPTERANS, HYMEN- 

 OPTERA (from vfir/v, a membrane, and 

 ■KTEpov, a wing). An order of mandib- 

 ulate insects, comprehending those 

 which have four membranous wings 

 with few nervures. Latreille divides 

 this order into the following sections 

 and tribes : 



1. TercbrayUia: Abdomen of the fe- 

 males furnished with a saw or borer. 



a. Securifera: Abdomen sessile, fur- 



nished with a saw ; larvae with 

 feet. 



b. Pupivora : Abdomen peduncula- 

 ted, furnished with a borer ; lar- 

 vae footless. 



2 Aculcata : Abdomen of the fe- 

 males armed with a sting. 



a. Heterogyna : Females wingless. 



b. Fossores: Females winged, wings 

 not folded ; basal joint of poste- 

 rior tarsi simple. 



c. Diploptera : Females winged, 

 wings folded. 



d. Mellifera : Females winged, 

 wings not folded ; posterior tar- 

 si enlarged, and converted into 

 a pollinigerous organ. 



HYPERSTHExXE. A species of 

 mineral resembling hornblend, with 

 little lime and twenty-four per cent, 

 iron. In some greenstone rocks it 

 takes the place of hornblend. 



HY'PERTROPHY. An unusual 

 increase in size of any organ of the 

 body. 



HYPOCHONDRIUM. The region 

 of the body under the cartilages of 

 the false ribs. The liver lies in the 

 right, and the spleen in the left hyp- 

 ochondrium. 



HYPOCRATERIFORM. Salver- 

 shaped. A corolla consisting nearly 

 entirely of a tube. 



HYPOGASTRIC REGION, HY- 

 POGASTRIUM (from vno,u7ider, and 



