4 Dr MacCulloch on Slack Leadfrom Cast-iron, 



These pieces of iron were cast cones, perforated with holes, 

 and about an inch thick, being used as strainers, to prevent 

 foreign substances from getting into the pipes. They had been 

 immersed in the porter for many years, no one knew how 

 many. On examining them, they appeared entire and un- 

 changed ; but some of them, instead of being iron, were en- 

 tirely of black lead ; and, in others, there was a thick coat of 

 that substance on each side, a little iron only remaining in the 

 middle. 



As this was then a new phenomenon in chemistry, I was in- 

 duced to repeat the experiment in the laboratory, and it was 

 attended with the same results, after some failures. An acci- 

 dent, however, occurring about this time, shewed me that the 

 fact was not so new as I had imagined, and I therefore took no 

 notice of it in public. Since that it has been observed by many 

 persons, who all probably imagined, with as good reason, that 

 they had made the same discovery. As many of these accounts 

 have appeared in your own Journal, I need not refer to them 

 more particularly. 



The circumstance to which I allude was the following, which 

 I happened to meet with in one of my journeys iu the Western 

 Islands. 



After Captain Roe had invented the diving-bell, he joined 

 Sir Archibald Grant, a great speculator of that day in coal- 

 mines and other matters, in an attempt to weigh the Florida, 

 one of the Spanish Armada, which had foundered off the coast 

 of Mull, near the entrance of Tobermory harbour ; she having 

 been taken by the natives, assisted by some treachery on the 

 part of the crew, which is said to have hung up the Captain at 

 the yard-arm. There her timbers are still lying. 



This attempt, which took place in 1740, was unsuccessful, as 

 far as related to the ship ; but some guns both of brass and 

 iron were brought up. The former, whether they belonged to 

 the Spanish vessel or not, had the mark of an English founder, 

 R. and J. Phillips, 1584, with a crown and E. R. on them. 

 The iron guns were deeply corroded, and on scraping them, it 

 was said that they were found so hot that they could not be 

 touched, and that they did not become cool till they had beea 

 &\vo or three hours exposed to the air. 



