196 Scientific Intelligence.— Arts, 
part. In this manner the strap forms two parallel bands, placed 
in a vertical position, and united above and below. Two sticks 
are passed between them, crossed horizontally ; and they are 
turned round several times. By this means the two bands are 
twisted and pressed against each other as strongly as possible ; 
and when the moving power ceases, they turn of themselves in 
the opposite direction. During this operation the leather is very 
sensibly heated ; fatty substances are then applied to it anew, 
with which it is fully impregnated, and at length acquires an 
extraordinary degree of pliancy. The leather thus prepared 
lasts for a very long time, and preserves its good qualities in all 
sorts of weather. — Bullet. Univers. Aug. 1825. 
51. Composition for the Covering of Buildings , hy M. Pew . 
— The composition proposed by the author is destined to form 
a sort of unalterable and incombustible mastich. For this pur- 
pose, he takes the hardest and purest limestone that he can find, 
free from sand, clay, or other heterogeneous matter. White 
marble is to be preferred, if it can be procured. This limestone 
is calcined in a reverberatory furnace ; it is then pulverised, and 
passed through a sieve. One part is taken by weight, and mix- 
ed with two parts of clay well baked, and similarly pulverised. 
This mixture must be made with great care. On the other hand, 
one part of calcined and pulverised sulphate of lime (gypsum) is 
taken, and two parts of clay, baked and pulverised, added to it. 
These two sorts of powder are then combined and incorporated, 
so as to produce a perfect mixture. The composition is pre- 
served for use in a dry place, sheltered from the air, where it 
keeps for a long time, without losing its properties. When it is 
to be used it is mixed with about a fourth part of its weight of 
water, which is gradually added, stirring it continually, until it 
forms a thick paste. This paste is spread upon the laths and 
joists of buildings, which it renders entirely incombustible. It 
becomes in time as hard as stone ; allows no moisture to pene- 
trate, and is not cracked by heat. When well prepared it will 
last for any length of time. The composition when still in a 
plastic state, will receive whatever colour it may be thought pro- 
per to give it. 
52. Mr TurreWs method of rendering Gravers capable of 
Engraving Steel-Plates. — Having been informed by his writing 
