Cotton-Grass, or Erhpko-rum, L. is a perennial, native genus of plants, consisting of five species, the principal of which are the following:

1. The angustifolium, or common; mon cotton-grass, moor-grass, moss-crops, or many-headed co ton-grass. It is found chiefly on marshes and bogs in the county of Stafford, on Birmingham-heath, and near Newport, Shropshire.— In the Island of Skye, in Scotland, this plant is useful to support cattle in the earlier part of the spring, before the other grasses are sufficiently grown. The poorer class of people stuff their pillows with the woolly down of this plant, and also employ it in making wicks for candles.

2. The polystachion, or broad-leaved cotton-grass, which grows in the marshy parts of the counties of Northampton ; Bedford, near Dunstable ; York, Cumberland ; and very common in Scotland.

Large tracts of ground are some-times covered with the white down fibres of this plant, which flowers from April to June ; and subsequently represents the snowy field of winter: its presence, however, indicates a soil productive of turf, or peat. • Neither cattle nor sheep relish this vegetable, the hairy seed-vessels of which vitiate the hay, insomuch that large conglobate masses have often been found in the stomachs of animals, that died in consequence of feeding on such provender.

Hence the necessity of collecting the down of the broad-leaved cotton-grass, both for preventing the injurious consequences to cattle, and converting it to the following useful purposes. The late Dr. GLEDITSCH, of Berlin, made a variety of curious experiments with this woolly substance; and found, that in combination with either sheep's wool, or cotton, it could be spun into a very strong and Uni-form yarn, from which were produced durable gloves, stockings, stuffs, and excellent cloth. He admits, however, that this downy material is more brittle than the fibrous integuments in which the seeds of the. sweet, or bay-leaved willow, are enveloped. Nevertheless, we have recently had an opportunity of ascertaining, and think it our duty to announce it to the public, as a fact worthy the at-tention of manufacturers, that both substances before-mentioned, may be prepared by a simple chemical process, in such a manner as to render them eminently tit for being mixed with improved animal wool, as well as cotton and silk, nay, even the refuse of flax and hemp. Clothiers, serge and stocking-makers, hatters, and all other artisans employed in this branch of staple manufactures, may perhaps find it their interest to obtain far-ther information on this important subject.