1829.] 



VarielieSf 



223 



those parts where friction takes place in 

 clocks, watches, and other fine mechanical 

 arrangements, has induced numerous per- 

 sons to endeavour so far to purify the oil as 

 to prevent or retard the injury occasioned to 

 the going of the machine as much as possi- 

 ble. Ulr. Hebert appears to have overcome 

 this difficulty all at once, by discarding the 

 oil altogether, and using instead well pre- 

 pared plumbago. He first prepares the 

 plumbago by repeatedly grinding and 

 washing it over, by which means the gritty 

 particles that occur, even in the best black 

 lead, are removed, and which, if allowed to 

 remain, would neutralize every advantage 

 the pure plumbago is found to give. This 

 done, the prepared substance is applied 

 v/ith a camel hair pencil, either in the state of 

 powder, or mixed up with a drop or two of 

 pure spirit of wine. It readily adheres to 

 the surface of a steel pivot, as well as to the 

 inside of the hole in which it runs, so that 

 the rubbing surfaces are no longer one 

 metal upon another, but plumbago upon 

 plumbago. These surfaces, by their mu- 

 tual action, speedily acquire a polish only 

 inferior to that of the diamond, and then 

 the retardation of the macliinc, from 

 friction, is reduced almost to nothing, and 

 wear and tear from this cause is totally pre- 

 vented. An astronomical clock of I\Ir. He- 

 bert's own making, of whicli the pivots, and 

 holes, and teeth of the escape wheel, had 

 been covered, on their rubbing parts with 

 line plumbago fourteen years ago, was 

 taken to pieces by a committee of the Society 

 of Arts and examined ; the surfaces of 

 plumbago were found to be for the most 

 part unbroken and highly polished, and 

 neither the pivots nor sockets appeared, on 

 examination with high magnifiers, to have 

 undergone the slightest degree of wear. 



Origin of the Solar System. — 31. Nic. 

 C'acciatorc, the eminent director of tlie ob- 

 servatory at Palermo, has endeavoured to 

 assign the cause of the movements of the 

 celestial bodies by combining the idea of his 

 predecessor Piazzi with those of La Place. 

 lie supposes that the planets owe their 

 origin to an explosion which took place in 

 tlic mass of the sun. In his system, the 

 matters projected in an aerifonn state, must 

 have first formed round the sun an immense 

 atmosphere, subjected to follow the rotatory 

 motion of this body. These, condensed 

 into different zones by cooling, the parts of 

 lliis fluid most distant from the sun must 

 have separated themselves from the rest of 

 the mass without removing from the solar 

 equator, and without ceasing to move in 

 the same direction. Their mutual attrac- 

 tion lias united them, and formed of them 

 solid Ijodies, tlie movements of translation 

 and of rotation ofv/liich are composed of all 

 the particular movements of the aggregated 

 particles. 



.trcounl of the E.vphsionof Slickensidcs. 

 — .Slickcnsides is a singular formation, 

 occurring in sonic perpendicular mineral 



veins, consisting of two imperceptible specu- 

 lar surfaces joined together without cohe- 

 sion ; they are sometimes composed of a 

 mixture of fluor carbonate of lime, galena, 

 blende, &c. ; at others, these surfaces are 

 thinly spread over with galena, as smooth 

 and shining as if polislied by art, and are 

 then termed looking-glass ore : they are 

 sometimes flat, at others waved ; sometimes 

 the waves in the same s])ecimen are both 

 perpendicular and horizontal, often in 

 wedge-shaped nodular masses of various 

 sizes dispersed in the veins. When their 

 edges occur in the face of the vein, on the 

 miner striking his pick into tlie vein they 

 separate in some districts without, in others 

 with a slight report, and in some of the 

 mines in the neighbourhood of Eyam, in 

 Derbyshire, with loud reports, particularly 

 in Cracking-hole Vein in Haycliffe title, 

 situated in the shell hmcstone beneath the 

 shale stratum, where, in the centre of the 

 vein termed a slack vein, was a small 

 white impalpable (not effervescing) powder, 

 called a mallion, a quarter of an indi thick, 

 which on being scratclied a loud explosion 

 immediately ensued, before wliicli explosion 

 a singing kind of noise w;is heard. By 

 setting a blast in the vein, at a short distance 

 from the maUion, after the blast was fired, 

 in a few minutes an explosion took place, 

 when a large quantity of the vein fell down. 

 In the year 1790, a loud explosion took 

 place from a slide joint of Slickensides, 

 going across, but not into the cheeks of the 

 vein containing the mallion, which caused, 

 on its being stirred, the loudest explosion, 

 and the largest quantity of vein materials to 

 come down. The vein there was four feet 

 wide, and three hundred yards from a dike 

 vein. The last great explosion was in the 

 year 1305. It has sometimes happened 

 that persons have been maimed, and even 

 killed by this phenomenon ; which, however, 

 has not been noticed in Slickensidcs, u'here 

 no shale is incumbent. Are not these ex- 

 plosions occasioned by combining by fric- 

 tion carbonic acid gas with tlie hydrogen 

 gas, which probably descends down a vein 

 from the shale, and wliich hovers in the 

 roofs of many subjacent caverns, and whicli 

 instantaneously ignites with a tremendous 

 explosion on the apjiroach of the flame of a 

 candle, and instances have occurred in 

 which they have proved fatal to human 

 life? 



Zoological Weather Glass In tlie 



southern parts of frermany there may fre- 

 quently be witnessed an amusing application 

 of zoological knowledge, for the pur]w.se of 

 prognosticating the weather. Two frogs of 

 the species rana urborcu are kept in a glass 

 jar about eighteen inches in heiglit and six 

 inclics in diameter, witli tlie depth of three 

 or four inches of water at the bottom, and a 

 small ladder, reaching to tlie to]) of the jar. 

 On the ai)proach of dry weather the frogs 

 njouiit the ladiler, but when wet weather is 

 expected (liey descend into (he water. 



