bones arrive at a certain degree of firmness and rigidity, which will not admit of farther extension by the motion of the blood. This period appears to take place between the age of eighteen and twenty-four; but in females, often one or two years earlier than in males. Lastly, it is remarkable, that the height or length of the human body varies at different parts of the day: thus, in the morning, after a long and refreshing sleep, an adult will be found one inch taller than he was in the preceding evening.
BOG, a quagmire covered with grass, but not firm enough to support a heavy body.
Various theories have been started, to account for the formation of bogs; but the most probable is, that they have originated from the roots of trees, and other decayed vegetables. Under some bogs of considerable depth, are to be seen the furrows of land once ploughed. The black bog is a solid, weighty substance, which cuts like butter, and is similar to rotten wood: but the red bog is of a lighter texture, though under it there is commonly a solid black stratum, which makes good fuel. Sound trees are found in both sorts of bogs, particularly in those of Ireland, which differ from the English, as the former sometimes present a perfect scenery of hill and dale, while the latter are mostly of a level surface. Of the most common spontaneous growth are, heath, bog-myrtle, rushes, and sedgy grass. Bogs are of various depths, some being found to be fifty feet deep, and others still deeper. A good method of draining boggy lands is, by deep trenches partly filled with stones, and covered with thorns and straw. A quantity of hard, dry earths, such as gravels, sands, chalks, stones, &c. is of great use in the improvement of bogs, as these substances serve to bind, fatten, and warm the soil, while they prevent springs from oozing up and overflowing the surface. By this method, boggy or marshy grounds may be improved so as to produce good grass.
BOHEA, a species of tea which is generally used for breakfast, with or without milk. It was formerly supposed, that infusions of this herb would sensibly satisfy the cravings of hunger, and afford a balsamic nutriment; for which reason they were highly recommended in decays and inward ulcerations, especially those of the lungs. But such virtues are no longer attributed to these, or any other tea-leaves: on the contrary, it is now generally understood, that all warm or hot liquors, and tea in particular, have a direct tendency to weaken the organs of digestion, and consequently to impair the appetite for food. From this circumstance, we apprehend, it has erroneously been inferred, that such beverage is nourishing.—See Tea.
BOILERS. Many ingenious vessels and utensils have, at different periods, been invented, with a view to facilitate the process of boiling, and save the consumption of fuel. In the latter respect, Count Rumford stands at the head of those experimental inquirers, who have directed their labours to the benefit of society; yet we must confess that there is still great room for improvement. One of the latest inventions in this department of domestic economy, is that of Mr. Tho. Rowntree, engine-maker, of Great Surrey-street, Blackfriars-road, who in 1798 ob-
obtained
