HOT 



313 



HUM 



purpose of steaming the pits when re- 

 quisite. If it is required that the circu- 

 lation should be confined to the first or 

 second pit nearest the boiler, the sluices 

 3, are closed, and those at 4 are 

 opened. These sluices are formed by 

 a metallic frame being substituted for 

 the tile at those points in which a small 

 metallic door works on a spindle. This 

 is attached to a rod passing up through 

 the earth, having a handle at the top, 

 just above the earth. In the winter, 

 when the thermometer stood at 23'^, 

 there was a bottom-heat of 90^, and of 

 SO^ on the surface of the pits then in 

 action, and of 73^ in the stove." — Gaid. 

 Chron. 



Open Gutters. — Mr. Griffin, gardener 

 to Mrs. Wells, of Cowley, near Exeter, 

 has published the following remarks 

 upon this mode of circulating hot- 

 water. 



'' The open trough, or gutter, may 

 be ap()lied to a boiler of any construc- 

 tion. The water (lows from the top of 

 the boiler, through a four-inch pipe, 

 into troughs made of cast iron, of the 

 following dimensions; inside measure 

 six inches wide at the top, three inches 

 and a half at the bottom, and seven 

 inches deep; the trough is constructed 

 in lengths three feet long, neatly fitted 

 together by a rivet in the bottom, and 

 one on each side near the top. The 

 water returns in a cast-iron pipe, three 

 inches in diameter. There are thin iron 

 lids or covers, of the same length at 

 each portion of the trough, to fit upon 

 the whole length of the apparatus, so 

 that the degree of humidity may be 

 regulated by making up some portions 

 of the covers, without disturbing the 

 others. The troughs or gutters might 

 be made of various materials, but I 

 prefer iron. The heat is diffused from 

 the surface of the trough or pipes, 

 nearly as quickly as it would be from 

 copper or zinc, and retains the heat 

 much longer. The width and depth of 

 the troughs should be varied according 

 to the plants intended to be grown in 

 the house. An orchidaceous house re- 

 quires a wider surface on the top than 

 those intended for the growth of erica; 

 and green-house plants generally. Dur- 

 ing the resting season of orchidaceous 

 plants, the atmosphere of the house is 

 easily kept less humid, by not removing 

 the whole or any part of the lids. 



" For vineries and peach-houses, it 



would answer exceedingly well, and 

 entirely eradicate the red spider; for 

 the trough can be covered when the 

 trees arc in (lower, and when the fruit 

 is approaching towards maturity. On 

 the other hand, during the growing 

 season you may maintain a regularly 

 humid atmosphere with less trouble 

 than by any other means. In a pine- 

 stove, forty feet Ions;, with a walk be- 

 tween the back wall and bark bed, the 

 trough being two feet from the level of 

 the walk, Mr. Gritiin says, ' I can com- 

 mand any degree of heat with much less 

 attention than is required for some 

 houses with a boiler of the same de- 

 scription, and equal power as regards 

 pipe.' " — Gnrd. Chron. 



HOUND'S-TONGUE. Cynoglossum. 



HOUSELEEK. Sempervivum. 



HOUSTONIA. Five species. Hardy 

 herbaceous. Division. Peat. 



HOVEA. Sixteen species. Green- 

 house evergreen shrubs. Young cut- 

 tings. Sandy loam and peat. 



IIOV'ENIA. Two species. Green- 

 house evergreen trees. Ripe cuttings. 

 Loam and peat. 



HOYA. Eight species. Stove ever- 

 green twiners. Cuttings. Light loam 

 and peat. 



HUDSONIA. Three species. Half- 

 hardy evergreen shrubs, llipe cuttings 

 and layers. Shaded peat soil. 



HUERNI.\. Eleven species. Stove 

 evergreen shrubs. Cuttings, dried for 

 a few days. Sandy loam and lime rubbish. 



HUGONIA. Two species. Stove 

 evergreen shrubs. Ripe Cuttings. 

 Loam, peat, and sand. 



HUMBLE-PLANT. Mi/nosa pndica. 



HUMtF.A clegans. Green-house bien- 

 nial. Seed. Common soil. 



HUMUS. When the putrefactive 

 process of plants is completed, there 

 remains a soft black mass, known as 

 vegetable mould, or humus. One hun- 

 dred parts of the humus of wheat 

 straw have of extractive or apotheme, 

 rather more than twenty-six parts, and 

 the residue is lime, peroxide of iron, 

 phosphate of lime, and carbonaceous 

 matter. This apotheme is identical 

 with the humic acid of Liebig, the ulmic 

 acid of Braconnot, and the geic acid of 

 Berzelius. It contains — 



Carbon 46.C 



Hydrogen 20.0 



Oxygen 33.4 



It was once believed, indeed is still 



