2t ;0 THE FARMER AT HOME. 



oases may be disadvantageous, on account of their being an escape of 

 carbonic acid, which gives rise to flatulency in the stomach and 

 bowels. By exposing the carbonate of magnesia to a strong heat for 

 a proper length of time, the carbonic acid is driven off, and the pure 

 magnesia remains, which is then termed pure, calcined or burnt mag- 

 nesia. Double the quantity of the carbonate is required to produce 

 the same effect as the calcined magnesia. 



MAGNETIC NEEDLE. A small bar of iron, to which, by 

 artificial means, the peculiar arrangement of the magnet has been 

 transferred, by which it points in the magnetic meridian ; and the 

 direction of this meridian being known, the course of ships at sea is 

 thereby determined. It also dips or inclines from the plane of the 

 horizon, pointing towards the apparent centre of a magnetic sphere, 

 existing, as it were, with the sphere of the earth, the varying poles 

 of which seem to be at right angles to the plane of the ecliptic. 



MAHOGANY. The mahogany tree is a native of the warmest 

 parts of America, and grows also in the islands of Cuba, Jamaica, 

 Hispaniola, and the Bahama islands. It abounded in the low lands 

 of Jamaica formerly, but it is now found only on hills, and places 

 difficult of access. This tree grows tall and straight, rising often sixty 

 feet from the spur to the limbs ; and is about four feet in diameter. 

 The foliage is a beautiful deep green, and the appearance made by 

 the whole tree very elegant. The flowers are of a reddish or saffron 

 color, and the fruit of an oval form, about the size of a turkey's egg. 

 Some of them have reached to a monstrous size, exceeding one hun- 

 dred feet in height. In felling these trees, the most beautiful part is 

 commonly left behind. The negro workmen raise a scaffolding of 

 four or five feet elevation from the ground, and hack up the trunk, 

 which they cut into balks. The part below, extending to the root, is 

 not only of larger diameter, but of a closer texture than the other 

 parts, most elegantly diversified with shades or clouds, or dotted like 

 ermine with spots : it takes the highest polish, with a singular lustre. 

 This part is only to be come at by digging below the spur, to the 

 depth of two or three feet, and cutting it through ; which is so labori- 

 ous an operation, that few attempt it, except they are curious in the 

 choice of their wood ; or to serve a particular purpose. 



The mahogany tree thrives in most soils, but varies in texture and 

 grain, according to the nature of the soil. On rocks, it is of a smaller 

 size ; but very hard and weighty, and of a close grain, and beauti- 

 fully shaded ; while the produce of the low and richer lands is ob- 

 served to be more light and porous, of a paler color, and open grain ; 

 and that of mixed soils to hold a medium between both. This con- 

 stitutes the difference between the Jamaica wood and that which is 

 collected from the coast pf Cuba and the Spanish Main : the former 

 is mostly found on rocky eminences ; the latter is cut in swampy soils, 

 near the sea coast. The superior value of the Jamaica wood, for 



