VOL. XLIV.] , PHILOSOPHICAL TKANSACTIONS. 305 



brass, whose distances from the point, directly under the apex of the obelisk, 

 were respectively equal to the lengths of the shadow at noon, on the several day* 

 of the year; as the same lengths decreased from the shortest day to the longest, 

 and again increased from the longest day to the shortest. 



After which the author mentions in a passage, greatly corrupted, and therefore 

 now almost unintelligible, that one Manilius, or Manlius, had added to the top 

 of the obelisk a gilded ball, the use of which was to make the shadow of the 

 extremity the more observable, as the middle part of the shadow of that globe 

 could readily be estimated, whereas the shadow of an apex would, at so great a 

 distance, be entirely imperceptible. 



Concerning Spelter, Melting Iron with Pit-coal; and 07i a Burning ffell at 

 Broseley. By the Rev. Mr. Mason, Woodwardian Professor at Cambridge, 

 and F. R. S. N° 482, p. 370. 



What spelter is, or what uses are already made of it, Mr. M. professes not to 

 know : but he believes it was never yet applied to so large a work as the cylinder 

 of a fire-engine, till Mr. Ford, of Colebrook Dale in Shropshire, did it with 

 success; it ran easier, and cast as true as brass, and bored full as well, or better, 

 when it had been warmed a little; while cold, it is as brittle as glass, but the 

 warmth of his hand soon made it so pliant, that he could wrap a shaving of it 

 round his finger like a bit of paper. This metal never rusts, and therefore 

 works better than iron, the rust of which, on the least intermission of working, 

 resists the motion of the piston. 



Several attempts have been made to run iron ore with pit-coal, he thinks it 

 has not succeeded anywhere, as we have had no account of its being practised; 

 but Mr. Ford, from iron ore and coal, both got in the same dale, makes iron 

 brittle or tough, as he pleases ; there being cannon thus cast so soft as to bear 

 turning like wrought iron. 



At Broseley, about a mile from the forementioned place, in the year 17 11, a 

 well was found, which burned with great violence, of which some account is 

 given in Philos. Trans. N** 334 ; but it has been many years lost. The poor 

 man, in whose land it was, missing the profit he used to have by showing it, 

 applied his utmost endeavours to recover it; but all in vain, till May last; when 

 attending to a rumbling noise under the ground, like what the former well made, 

 though in a lower situation, and about 30 yards nearer to the river, he happened 

 to hit on it again. 



The well for 4 or 5 feet deep is 6 or 7 feet wide; within that is another less 

 hole, of like depth, dug in the clay; in the bottom of which is placed a cylin- 

 dric earthen vessel, of about 4 or 5 inches diameter at the mouth, having the 

 bottom taken off, and the sides well fixed in the clay rammed close about it, 



VOL. IX. Rr 



