WHEAT-GRASS. 



rhizome, strikes so deeply and widely as to be 

 very difficult of extirpation. It is, in fact, an ; 

 underground stem, vivacious, and consequently j 

 shooting up stems and leaves at every joint. 

 The stem above ground is slender, 2 feet high, 

 and leafy. Leaves linear, flat, of a dull, some- 

 what glaucous green, most numerous on the 

 lower part of the stems. But the plant is so 

 well known that it requires no description. 

 Forking out the roots after the plough is doubt- 

 less the best mode of extirpating this noxious 

 weed ; but the process must not be discontinued 

 while a particle of the root-stock is suspected 

 to remain in the soil, as the least portion will 

 grow, and the land being so much broken and 

 loosened by the operation, gives double encou- 

 ragement for the rapid growth of the plant. It 

 does not thrive well when combined with other 

 grasses, but is naturally more common in 

 hnL'i-s. The root-stock contains a large pro- 

 portion of nutritive matter; it is esteemed 

 abroad for feeding horses. At Naples the root- 

 stocks are collected in large quantities for this 

 purpose, and brought to market. The nutritive 

 matter from the leaves contains an excess of 

 bitter extractive and saline matters. Dogs eat 

 the leavc^, and also those of the Hohnis avena- 

 ctus, to excite vomiting; hence it is sometimes 

 called dog's grass, and in other places bears 

 the name of quitch or quicks. See Corrn. 



3. Fibrous-rooted, or bearded wheat-grass 

 ('/'. rintiiiKtn). This differs essentially from 

 the common couch-grass last described, in 

 having the root fibrous, without a rhizome. It 

 {.rrou > in woods and shady hedges on a chalky 

 or limestone soil. The stems are 2 feet high, 

 very smooth. Leaves nearly upright, lanceo- 

 late, taper-pointed, thin, flai, bright green, rough 

 on both sides. As this grass yields a large 

 Mipply of early spring herbage, and produces 

 a suiiiciency of seeds, which vegetate quickly 

 on all soils except such as are tenacious or re- 

 tentive of moisture, it might be cultivated to 

 advantage on soils of an inferior quality in- 

 stead f rye-grass. But for soils of the best 

 quality it does not, as yet, uphold a sufficient 

 claim, the awns of the spike being objectiona- 

 ble, and the produce of the latter-math very in- 

 considerable. 



4. Crested wheat-grass (T. rristu(nm'), a na- 

 tive of Scotland. The roots of this species 

 consist of several long, strong woolly fibres, 

 suited to a sandy soil. The culms are ascend- 

 ing, 12 or 18 inches high, simple, rigid, slen- 

 der, leafy ; hairy at the top. This grass seems 

 well adapted, from its comparative merits, for 

 culture on light heath soils ; the produce of 

 early herbaee in the spring being superior to 

 most of the alpine grasses, or those which 

 affect sandy dry soils. The latter-math is pro- 

 ductive, and very nutritious. It flowers about 

 the second week of July, and the seed is ripe 

 about the end of August 



5 Dwarf sea wheat-grass (T. loliaceum}. 

 This is an annual species, growing on the 

 sandy sea-coast, flowering in June and July. 

 The root is formed of many long downy fibres. 

 Stem rigid and wiry, branched from the bottom, 

 generally 2 or 3 inches high, but various in 

 luxuriance, leafy, very smooth, and polished, 



WHEEL. 



erect or decumbent. Leaves linear, acute 

 nearly smooth, involute when dry. 



WHEEL. A circular piece of wood, me. 

 tal, or other substance, that revolves on an 

 axis. It consists of three principal parts, 

 the nave, heel, or the centre; the spokes or 

 radii, and the periphery or ring. The strength 

 of the wheel depends much on the framing 

 and the arrangement of the spokes, every one 

 of which should stand perpendicularly to the 

 nave. In England and other parts of Europe, 

 the elm is considered the best wood for making 

 naves, as it bears the cutting of the mortices 

 truer than any other. See ELM. In making 

 wheels, after they are loosely put together, they 

 are either left to season in a current of air for 

 some weeks, or they are exposed to a heat of 

 140 Fah. in a kiln. After this they are exa- 

 mined, and if every thing is correct, the tire or 

 iron hoop is put on, whether made of one hoop 

 or separate pieces. Some years since a patent 

 was taken out in England by Mr. T. Jones for 

 making iron wheels, many of which are now 

 in use. These wheels are not conical, nor what 

 is termed dished, but cylindrical, which enables 

 them to run lighter and also prove less destruc- 

 tive to roads. They are not heavier than 

 wooden wheels, they require less draught, and 

 are more durable, Some improvements ha\ 3 

 been made on Mr. Jones's wheel by Mr. Wil- 

 liam Howard, but the merits of this have not 

 yet been fully proved. 



The utility of wheels to carriages may be 

 said to be twofold ; namely, by diminishing or 

 more easily overcoming the resistance or fric- 

 tion from the carriage, and more easily over- 

 coming obstacles in the road. In the first the 

 friction on the ground is transferred, in some 

 degree, from the outer surface of the wheel ';o 

 its nave and axle, and in the latter they serve 

 easily to raise the carriage over obstacles and 

 asperities met with on the roads. In both 

 these cases the height of the wheel is of mate- 

 rial consideration ; as the spokes act as levers, 

 the top of an obstacle being the fulcrum, their 

 length enables the carriage more easily to sur- 

 mount them, and the greater proportion of the 

 wheel to the axle serves more easily to dimi- 

 nish or to overcome the friction of an axle, as 

 has been shown by Jacob in his work on Wfieel 

 Carriages. 



Carriages with four wheels are much more 

 advantageous than carriages with two wheels, 

 as carts ; for with two wheels, it is plain, the 

 tiller horse carries part of the weight in one 

 way or other; in going down hill the weight 

 bears upon the horse, and in going up hill the 

 weight falls the other way and lifts the horse, 

 which is still worse. Besides, as the wheels 

 sink into the holes in the roads, sometimes on 

 one side, sometimes on the other, the shafts 

 strike against the tiller's sides, which destroys 

 many horses ; moreover, when one of th* 

 wheels sinks into a hole or rut, half the weight 

 falls that way, which endangers the ovsrturn- 

 ing of the carriage. 



With respect to the utility of broad wheeii 

 in amending and preserving the roads, it ha.{ 

 been so long and generally acknowledged as to 

 have occasioned the legislature to onforce their 



1151 



