VOL. XXX.] PHILOSOPHICAL TRANSACTIONS. 427 



I found that an ounce of silk-balls would make about a drachm of fine silk. 

 But to be more certain, I weighed out 12 lb. of silk-balls at 4 times, and told 

 the balls in every 3 lb. as follows, viz. 



The first 3 lb. contained 812 balls — the second 3 lb. contained 842 balls — the 

 third 3 lb. contained 797 balls — the fourth 3 lb. contained 868. So that the 

 whole 12 lb. weight contained 3319 balls. 



Which when wound off, was found to yield and make 1 lb. and 1 oz. or 17 

 oz. of fine silk, and about 7 Oz. of coarse refuse unwound, in all l-^lb. of 

 Avoirdupois weight, or 2 lb. Troy; which is as great or greater making or yield- 

 ing as in any part of the world, and the silk as fine. I showed it to a noted 

 silk broker, who said it was Italian silk, not knowing it was made in England, 

 and worth about 20 shillings per lb. 



Now on this experiment finding that 3319 silk-balls would make 1 lb. and 

 J oz. of fine silk. I was desirous to know what quantity of silk might be ex- 

 pected from the worms hatched from 1 oz. of eggs. For this I made use of 

 the following method : by often weighing and telling I found that 100 eggs 

 weighed but 1 grain; so that if I grain contains 100, a scruple must contain 

 2003, and a drachm 6000, and an ounce, at 8 drachms to the ounce, must con- 

 tain 48000 eggs. Now if every egg hatch a worm, and every worm makes a 

 silk-ball, there must be from 1 oz. 480O0 silk-balls; and if 3319 balls will make 

 1 lb. and I oz. of fine silk, then 48000 silk-balls will make 15 lb. and 6 oz. of 

 Avoirdupois weight, in fine silk, or 18 lb. and 8 oz. of Troy weight. And in 

 the same proportion 1 lb. of silk-worms' eggs will produce worms sufiicient to 

 make above 180 lb. of silk. But allowing for casualties, and supposing but 

 12 lb. of fine silk made from the worms and their silk-balls, produced from 1 oz. 

 of silk-worms' eggs; it will be found much to exceed most countries, according 

 to Augustino Gallo's computation; for he says, that in the southern parts of 

 France, viz. Languedoc and Provence, they make only 7 or 8 lb. of silk from 

 silk-worms hatched from 1 oz. of eggs; and in Brescia in Italy, only 8, 9, or 

 10 lb. of silk from 1 oz; only in Calabria, where the silk-worms and their eggs 

 are larger, they make 11 or 12 lb. of silk from 1 oz. of eggs. 



Firo Celeberrimo, Ricliardo Mead, M. D. Coll. Med. Lond. et S. R. S. S. P, D. 

 Jacobus Jurin, M.D. et R.S.S. N° 362, p. lOSp. 



Dr. Jurin's rejoinder to Dr. Keill, of which it seemed unnecessary to insert 

 a translation, for the reasons before-mentioned at p. 3/5 of the present vol. 



3 I 2 



