334 I'HILOSOPHICAL TRANSACTIONS. [aNNO 1729. 



pellucid crystallizations of spar, it is called bastard cauk. There are other bodies 

 mixed in the mines with lead ore ; but Mr. M. did not meet with them. 



When the ore is brought up from the mine, it is broken to pieces, that the 

 spar, cauk, or other bodies which adhere to it, may be more easily separated. 

 It is then thrown into a large sieve and washed, and so further purified from 

 extraneous bodies. After this, it is carried to the furnace, to be smelted. The 

 furnace, which Mr. M. saw near Worksworth, was very rude and simple, con- 

 sisting only of some large rough stones, placed in such a manner as to form a 

 square cavity, into which the ore and coals are thrown stratum super stratum ; 

 two great bellows continually blowing the fire, being moved alternately by 

 water. He saw no other fuel used on this occasion, but dried sticks, which 

 they call white coal. Mr. Ray informs us, in his Collection of English Words, 

 ed. !2, p. 174, that they use both white and black coal, or charcoal, in Cardi- 

 ganshire ; perhaps because that ore is harder to flux ; the charcoal making a 

 more vehement fire. They generally throw in some spar along with the ore, 

 which it is thought, by imbibing the sulphur, makes it flux more easily. They 

 frequently throw in also some coak, or cinders of pit-coal, because they think 

 it attracts the dross, and so makes it separate easier from the lead. When the 

 ore is melted, it runs out at an opening in the bottom part of the front of the 

 furnace, through a small channel made for that purpose, into a cylindrical vessel, 

 out of which it is laded into the mould. The dross of the ore, on smelting, is 

 called slag. This slag is afterwards smelted again with coak only, and the lead 

 obtained from it is called slag-lead. Their way of making red-lead is the same 

 with Mr. Ray's account, ibid. p. 200 ; only they use three parts of lead, and one 

 of slag-lead ; and think that the red-lead thus made, is better than if made 

 without slag-lead. 



The Difference of Longitude, in Time, of diverse Places, computed from 

 Observations of the Eclipses of Jupiter's Satellites. Bi/ the Rev. Mr. 

 Derham, F.R.S. N° 407, p. 33. 



Rome and Lisbon: l''24'"46^ 1 25 34; 1 26 34; 1 29 0; J 26 44; I 26 54; 

 1 28 11. — Rome and Paris: O'' 39"" 48'; O 40 50 ; O 36 16; O 38 56; 

 40 17. — Rome and Ingolstad : 0** 2"" 5P; O 4 1. — Rome and Bologne : 

 O^ S"* 45'; 2 16; O 4 45; O 4 14. — RomeandKew: O" 45"" 47^. — Rome 

 and Wansted : 0^ 49*" 10'. — Rome and Upminster: O'' 47"' 28'. — Rome and 

 Southwick in Northamptonshire: O'' 47"^ 58*. — Urbino and Lisbon: l'' 28™ 57'. 

 — Paris and Lisbon : O*' 45"' 4d' ; O 45 44. — Paris and Bologne : O'' 34'" SC ; 

 O 34 O; 38 32. — Ingolstad and Lisbon: l'' 22'" 53'; 1 23 21. — Ingolstad 

 and St. Quirico : O*' l'"20'; O 1 40. — Ingolstad and Bologne: O'' 1"' 53'. — 



