VOL. XVII.J PHILOSOPHICAL TRANSACTIONS. 573 



after the precept above delivered ; that is, not only boil the iron in its own sow- 

 metal, or liquid iron, but hammer it also, and after that quench it in cold 

 water. 



As to the steeling of their tools, they boiled them in sow-metal, to such a 

 degree of hardness or temper as was requisite, and did not afterwards hammer 

 them. And this seems to be implied in the phrase densare ; for although it be 

 generally said, that iron is purged and refined for the making of steel, yet ac- 

 cording to the last and truest process, the matter is plainly otherwise; for iron 

 this way made into steel, becomes a kind of electrum, and is filled with an ex- 

 ceeding brittle and hard body of its own nature ; iron being spongy and not 

 close ; for which purpose, therefore, the word densare is by Pliny aptly and 

 elegantly used. And this way was used when the strongest temper and hard- 

 ness was required, as for picks and anvils. For which there might be several 

 reasons given ; at first, that it is easier to work iron than steel, into any figure, 

 that being far softer and more ductile and loose : again it is certain that iron 

 by ignition is spoiled or corrupted, so that the oftener it is pCirged, though it 

 were steel, it would the more relent. Whence the ancients knowing well, that 

 in making their tools of steel, they must considerably loosen it, and abate of 

 their temper ; they therefore first shaped them, and then gave them a strong 

 body of steel and temper together, and so had nothing else to do, but to finish 

 them on the grind- stone and hone, to set the point or edge. 



A Description of certain Shells found in the East Indies. Communicated hy 

 Mr. fVitzen to Dr. Lister, and by him to the Editor, with some Remarks of 

 his own. N° 203, p. 870. 



There are found on the coasts of Malabar and Ceylon certain cockles or 

 shells, containing a fish that lives in the bottom of the sea, fixed to the body 

 of the shell; and, at a certain season of the year, they cast their seed, which 

 produces a kind of matrix or sack, of about 12 inches in length;* this long 

 body, which is wrinkled like an andouille or sausage, is filled with a great num- 

 ber of round cells, which are so many matrices, each producing its little shell- 

 fish ; which quit not their cells till they are grown to such a size and maturity, 

 as their weight breaks them off and loosens them from their cells, and so from 

 their common matrix, which remains fastened to the bottom of the sea by the 

 great end, the other end moving about freely in the water, which is flexible 

 every way like an andouille. This matrix has a kind of back-part and belly ; 



• Murex canaliculatus. Linn. The shells of the genera of murex and buccinura produce their 

 young in the manner here described, viz. imbedded in the cell of a long ovarium, or receptacle. 



