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LETTER IV.

Contains an important Discovery for the Im-provement of Worm-Pitch , with salesfor the better Security of Ships Bottoms.

Sir,

M Y Residence in this Kingdom hasgiven me frequent Opportunity ofdiscoursing with different Persons concernedin preparing Pitch for the Security of ShipsBottoms against Worms, and from thenceit is vulgarly called Worm-pitch j but so in-effectual are their best Methods, that all ofthem acknowledge, they cannot find out anyMixture that will so cohere with the Pitch tothe Wood, as to be a sufficient Guard againstthose pernicious Animals ; and thereforethought proper to consult me, whetherthere was any chymical or natural Body,on being mixed with Pitch , would so co-here to the Wood, as not to be destroyed orinjured by any Sea-water, and rendered im-possible for the Worms to penetrate throughit. This appearing to me a Matter of thegreatest Consequence, put me immediatelyupon Inquiry, what were the Ingredientsthey had hitherto made use of in theirMixture with the Pitch ; and the best In-formation I could get was, that it consistedof Chalk, Brick-dust, the Caput mortuumof Iron Vitriol (which is an Earth of ayeddifh-brown Colour) Soot, powdered

Glass,