1^ Sdentijic iMeUigenve, [Maiich> 



£ Mg S* + 2 Aq, in case the bituminous natter h considered at 

 foreign to the chemical composition. 



In conseciuence of the singular property of this mineral of tlie 

 change of colour when exposed to heat, from white to dark and from 

 dark to white again, the name pyralloUt, formed of the Greek wordf 

 ^S and «>^of, was given to it. 



II. Milliner IntelU}rence. 



At the latter end of December last, the third of the new steam 

 ■engines erected on the Const»lidaled mines near Redruth, in Cornwall, 

 was ]>ut to work : and as two of these machines are of a larger siz^ 

 than was ever before attempted, and as the concern is one of great 

 iBxtent and interest, some account of it may be acceptable to our 

 readers. 



'i lie undertaking includes four or five copper mines nearly adjoin*" 

 ing, and on the sanie veins, formerly worked very profitably in distinct 

 portions, until owmg to difficulties in pumping the water, and other 

 circumstances, they were gradually abandoned about 16 years since. 



The improvement in the use of steam power since that period is 9 

 prominent reason for expecting advantage to tho-<e who have had the 

 spirit to renew the workings, though there are many others which are 

 important, such as increased gkill in the management of mining pro- 

 cesses, and a reduction in the cost of labour and those materials which 

 are most largely consumed. The present con^pany have engaged a 

 capital of about 65,(X)()/. in the concern, and tlie whole is under the 

 management of Capt. William Davey and Mr. John Taylor. 



The extent of underground workings to be drained is very consider* 

 able, running for about a mile in length, and reaching at the lowest 

 part to a depth of about ISO fathoms under the adit, or level by which 

 jjie water is discharged towards the sea. 



To keep the whole of these excavations dry, and to enable the minei 

 to be sunk deeper, three engines have been erected by Mr Arthur 

 liVoolf One at the western extremity of the ground having a cylinder 

 of 70 inches diameter, which wo>ks a pump about 60 fathoms deep, 

 and two others, which we mean particularly to notice, are situated one 

 near the centre, and the other at the eastern end of the concern. 



These engines have cylinders of 90 inches diameter, the pistoni 

 make a stroke of 10 feet in the cylinder, and the centre of the beamt 

 is so fixed that the rods make an eight foot stroke in the pumps; thu» 

 they are able, at the commion pressure, to raise a load of 8.5,000 lbs. 

 Each of the engines is furnished with six wrought-iron boilers fo»* pro- 

 ducing high pressure steam, which is applied in the mode usually called 

 expansive by engineers, and is condensed in the common manner. 



Three boilers are connected so as to be heated by two fires, and are 

 sufficient to work the engine, leaving three others to be applied when 

 those which have been in use are cleansing or repairing 



These immense engines are executed in a very beautiful manner, and 

 exhibit remarkable instances of accurate workmanship and sound cal- 

 culation. J hough they exceed in power all others that have been 

 before constructed, and of course every part is of a dimension for which 

 Hiere is no precedent, yet each has, from the first, performed its office 

 aright, and the combination i« no perfect that the motions are equabiei 



