256 



Isothermal Lines. — To Prevent the Decay of Wood. Vol. VII. 



Isothermal Lines, 



Are those circuits around the earth, 

 where equal degrees of heat are experi- 

 enced. These lines are parallel each side 

 of the Equator, until the 22nd or 23d degree 

 of latitude ; at those parallels they begin to 

 diverge, and at 36 degrees and 40 degrees, 

 begin to be altogether irregular. In the 

 Northern hemisphere, one line of equal an- 

 nual temperature, runs through Rome and 

 Florence, in latitude 43 degrees north; and 

 through Raleigh, in North Carolina, in lati- 

 tude 36 degrees ; and through the Nether- 

 lands, latitude 51 degrees ; and Boston, in 

 New England, latitude 42 degrees. Edin- 

 burgh, in latitude 55 degrees, averages also 

 with Boston. Ulco, in Lapland, latitude 66 

 degrees, ranges with Lake Winnepeg, in 

 latitude 54 degrees. M. Kupffer, the Rus- 

 sian traveller, states that the temperature of 

 the air and soil varies the most rapidly, near 

 and beyond the 45th degree of North lati- 

 tude in America and Europe. The differ- 

 ence will be more readily appreciated, by 

 comparing Edinburgh, with all its elegance 

 and luxuries, its palaces and halls of learn- 

 ing, its gifted scholars and polished society, 

 with Labrador in the same parallel of lati- 

 tude, on the eastern side of the West conti- 

 nent, locked in the silent thraldom of icy 

 desolation; inhabited by a few straggling 

 Esquimaux, in huts of snow, with no other 

 clothing than the skins of wild beasts, and 

 depending for subsistence on sea-dogs, and 

 other ocean monsters. 



The heat and weight of the atmosphere 

 diminish, as we ascend from the level of the 

 sea. These facts are proved by the obser- 

 vation of travellers, ascent in balloons, by 

 the zones of vegetation on the sides of 

 mountains, by the rarity and want of elas- 

 ticity in the air, and by the excessive cold 

 at great elevations, as well on those under 

 the line, as those near the pole. At the foot 

 of mountains, under the Equator, spring the 

 fruits and flowers of the tropics; then fol- 

 lows a zone of the olive and the vine — then 

 the broad leaved forests — then the fir and the 

 pine — then the dwarf willows, stunted shrubs, 

 evergreens and mosses ; and last, the crests 

 of never changing snow. 



There are yet other known causes of the 

 variations of temperature, but why the air in 

 any given place should be mild and genial 

 one day, and chilled by frost, or scorched by 

 heat, on the next day following; or why one 

 period should be occupied with one extreme, 

 and the succeeding by another; or why one 

 season should be racked with all extremes, 

 in quick succession, are mysteries which 

 neither chemistry, mathematics, nor natural 



philosophy have ever yet penetrated, or re- 

 vealed. Electricity is known to have a 

 powerful agency in atmospherical phenom- 

 ena, and doubtless extends its invisible influ- 

 ence over every part of organised matter. It 

 seems to be a kindred element with heat, 

 and what are now the obscure results of 

 their joint action, may at some future day, 

 resolve the mysteries of meteorology, in 

 connection with the variations of tempera- 

 ture. — Hunt's Magazine. 



May, 1842. 



To Prevent the Decay of Wood. 



Take twelve ounces of rosin and eight 

 ounces of roll brimstone, each coarsely pow- 

 dered, and three gallons of train-oil. Heat 

 them slowly, gradually adding four ounces 

 of bees'-wax, cut in small bits. Frequently 

 stir the liquor, which, as soon as the solid 

 ingredients are dissolved, will be fit for use. 

 What remains unused, will become solid on 

 cooling, and may be remelted on subsequent 

 occasions. When it is fit for use, add as 

 much Spanish crown, or red or yellow ocre, 

 or any colour you want, first ground fine in 

 some of the oil, as will give the shade you 

 want; then lay it on with a brush as hot and 

 thin as you can ; some days after the first 

 coat is dried, give it a second. It will pre- 

 serve plank for ages, and keep the weather 

 from driving through brick-work. Common 

 white paint may be used on top of it, if re- 

 quired, for the sake of appearance. Two 

 coats should always be given ; and in all 

 compound machinery, the separate parts 

 should be so varnished, before they are put 

 together ; after which, it will be prudent to 

 give a third coating to the joints, or to any 

 other part which is peculiarly exposed to 

 the action of moisture; such as water-shoots, 

 flood-gates, the beds of carts, the tops of 

 posts, and all timber which is near, or within 

 the ground. Each coat should be dry before 

 the parts are joined, or the last coat applied. 

 The composition should be applied when the 

 wood is perfectly dry. It is necessary to 

 mention that compositions made of hot. oil, 

 should, for the sake of security, be heated 

 in metal ic vessels in the open air. For 

 when oil is brought to the boiling point, or 

 600° of Fahrenheit, the vapour catches fire; 

 and though a lower degree of temperature 

 should be used in this process, it is not al- 

 ways possible to regulate the heat, or to 

 prevent the overflowing of the materials; in 

 eithei of which cases, were the melting 

 performed in a house, fatal accidents might 

 happen. — Archives of Useful Knowledge. 



