BOL 



BOL 



of the melting point of solids, that it is 

 capable of being varied considerably by 

 altering the situation of the bouy. Thus, 

 water may be cooled down considerably 

 lower than 32 without freezing. The 

 boiling point is stdl less fixed, depending 

 entirely on the degree of pressure to 

 which the liquid to be boiled is exposed. 

 If we diminish the pressure, the liquid 

 boil-, at a lower temperature ; if we in- 

 crease it, a higher temperature is neces- 

 sary to produce ebullition. From the ex- 

 periments of Professor Robinson, it ap- 

 pears that in a vacuum, all liquids boil 

 about 145 lower than in the open air, 

 under a pressure of 30 inches of mercu- 

 ry ; therefore water would boil in va- 

 cuo at 67, and alcohol at 34. In a Pa- 

 pin's digester, the temperature of water 

 may be raised to 300, or even 400, with- 

 out ebullition; but the instant that this 

 great pressure is removed, the boiling 

 commences with prodigious violence. 



BOLETUS, in botany, so called from 

 its globular form, characterised by Lin- 

 naeus as a horizontal fungus ; porous or 

 punched, with lobes underneath. In 

 the fourteenth edition of the " Systema 

 Naturae," only twenty-one species are re- 

 cited, eleven of which are parasitical and 

 stemless, the rest are stipitated. From B. 

 igniarius is prepared the amadou, com- 

 monly used on the continent for tinder, 

 to receive the spark struck from the 

 steel by the flint, and the agaric, for stop- 

 ping haemorrhage in amputations, &c. 



BOLT, among builders, an iron fasten- 

 ing fixed to doors and windows. They 

 are generally distinguished into three 

 kinds, viz. plate, round, and spring bolts. 



BOLTS, in gunnery, are of several sorts, 

 as, 1. Transum bolts, that go between the 

 cheeks of a gun carriage, to strengthen 

 the transums. 2. Prise bolts, the large 

 knobs of iron on the cheeks of a carriage, 

 which keep the hand-spike from sliding 

 when it is poised up the breech of a 

 piece. 3. Traverse bolts, the two short 

 bolts that, being put one in each end of a 

 mortar carriage, serve to traverse her. 

 4. Bracket bolts, the bolts that go through 

 the cheeks of a mortar, and by the help of 

 quoins keep her fixed at the given ele- 

 vation. And, 5, Bed bolts, the four bolts 

 that fasten the brackets of a mortar to the 

 bed. 



BOLTS in a ship, are iron pins, of which 

 there are several sorts, according to their 

 different make and uses. Such are, drive 

 bolts, used to drive out others ; ray bolts, 

 with jags or barbs on each side to keep 

 them from flying out of their holes ; 

 clench bolts, which are clenched with 



rivetting hammers ; forelock bolts, which 

 have at the end a forelock of iron driv- 

 en in, to keep them from starting back i 

 set bolls, used for forcing the planks and 

 bringing them close together; fend or 

 fender bolts, made with long and thick 

 heads, and struck into the uttermost 

 bends of the ship, to save her sides from 

 bruises ; and rings bolts, used for bring- 

 ing to of the planks, and those parts 

 whereto are fastened the breeches and 

 tackles of the guns. 



There are various inventions for driv- 

 ing bolts into ships, and others for draw- 

 ing them out ; we shall describe one by 

 Mr. H. Phillips, for driving copper bolts 

 into ships, for which he received the gold 

 medal from the Society of Arts, &.c. in the 

 Adelphi. The instrument employed for 

 driving the bolts consists of a hollow tube, 

 formed from separated pieces of cast iron, 

 which are placed upon the heads of each 

 other, and firmly held thereto by iron cir- 

 cles or rings over the joints of the tube : 

 the lowest ring is pointed, to keep the 

 tube steady upon the wood ; the bolt, be- 

 ing entered into the end of the hole bored 

 in the wood of the ship, and completely 

 covered by the iron tube, is driven for- 

 wards within the cylinder by an iron or 

 steel punch placed against the head of the 

 bolt, which punch is struck by a mall; 

 and as the bolt goes farther into the wood, 

 part of the tube is unscrewed and taken 

 off, till the bolt is driven home into its 

 place up to the head. 



The tubes are about five inches in cir- 

 cumference, and will admit a bolt of seven- 

 eighths of an inch in diameter 



References to Plate, Life Boats, &?c. 



Fig. 4. A, the copper bolt, with one 

 end entered in to the wood previous to fix- 

 ing the tube. 



B, a piece of timber or ship's side into 

 which the boh is intended to be driven. 



Fig. 5. C, C, C, C, the parts of the iron 

 tube fastened together, ready to be put 

 on the bolt A. 



D, D, I), D, iron or brass rings, with 

 thumb screws placed over the joints of 

 the tube, to hold them firm together. 



E, E, E, E, the thumb screws, which 

 keep the rings and tube firm in their pro- 

 per places. 



F, two points formed on the lower ring; 

 they are to slick into the timber, and to 

 enable the tube to be held firm in it* 

 place. 



Fig. 6. Shews the separation of the 

 parts of the tube, which is effected by 

 slackening the thumb screws and rings. 



