Gypsum, or Plaster of Paris, is a sulphate of lime, composed of- -

Sulphuric acid.....43

Lime ........33

Water........24

It has been employed advantageously as a manure to the turnip and potato, at the rate of 3 cwt. per acre. Potato sets are frequently rolled in it when pulverized. It has been recommended to be sprinkled in stables, and to be mixed with dunghills, "to fix the ammonia," as it is popularly termed. That am-moniacal fumes are given out from the urine of horses, and from decomposing dungheaps, is true; but it is quite as true, that sulphate of lime thus employed will not detain a thousandth part of them, owing to the sulphuric acid having a greater affinity for the ammonia than for lime, and carbonic acid having a greater affinity for lime than for ammonia. And it is also true, that all the ammonia lost in fumes from a dunghill might be more readily and as cheaply restored to it by mixing with it, when dug into the soil, a little of the am-moniacal liquor from the gas works. Gypsum is extensively used in Pennsylvania and in many cases with the best results. For its introduction originally we are indebted to the late Judge Peters; from a "short notice" of whom, by Samuel Breck, Esq., we extract the following:

"As a practical farmer, Mr. Peters had from time to time communicated the results of the experiments made at Belmont, to such of his neighbours as chose to profit by them; but he had not written much, if anything, upon agriculture, before the year 1797. His first publication was then made, and contained a statement of facts and opinions in relation to the use of Gypsum. This pamphlet circulated widely, and produced such a change in husbandry, by introducing the culture of clover, and other artificial grasses, as gave, we all know, a magical increase to the value of farms. Estates which until then were unable to maintain stock, for want of winter fodder, and summer pasture, were suddenly brought into culture, and made productive. Formerly, on a farm destitute of natural meadow, no stock could be supported; and even where natural meadow existed, the barn yard was exhausted to keep up sufficient fertility, (in the absence of irrigation,) to feed a very few horses and black cattle.

"Such was the situation of our husbandry, for some years after the revolution. It is proper to advert to it, that we may understand the full extent of our obligation to the Judge. In the year 1770, he was shown the effects of gypsum on clover, in a city lot, occupied by Mr. Jacob Barge, on the commons of Philadelphia.

"The secret of its powerful agency came from Germany, where it was accidentally discovered. Mr. Peters obtained a small quantity, which he used successfully, and gradually promoted its consumption, until, by his example, and his publications, the importation from Nova Scotia alone, into the single port of Philadelphia, increased to the enormous amount of fourteen thousand tons annually. This was before the discovery of that fossil in the United States.

"Inquire in the counties of Chester, Lancaster, and others around us, where clover is so beneficially cultivated, how much is due to that excellent man, for the great pains he took to extend the use of gypsum ? On this subject, I very recently transmitted to the Judge, a testimonial of gratitude from one of the most intelligent persons of Lancaster; who unhesitatingly ascribes to Mr. Peters' book on plaster, and his other agricultural essays, the merit of having produced a good part of the rich cultivation, for which that country is so celebrated".