ays 
Description of a Screw Press, 
numbers of plates, particularly when the iron is short or 
brittle, are broken near the mortiees by missing the 
stroke of the hammer, which must be used with great 
force. 
Advantage gained in laying my Tram-Plates in Com- 
parison with other Modes. 
L, s . A, 
Nails used in a mile, 3520 of 3 in the pound, 
at per lb. . . . 19 11 0 
Nails lost or defective, computed at per mile 10 0 
Plugs with their loss . . . .650 
By breakage of rails, average from experience 7 10 0 
Lessened by labour in block laying, calcu- 
lated at only two pence per yard . . 14? 13 - 4 
By breakage of blocks . . . .10 0 
IA9 19 4 
This calculation does not take in annual loss of nails,* 
and breakage of blocks, which is considerable. 
No. 73. 
Description of a Screiv Press with an expanding Power 
By Mr, William Bowler. 
(With an engraving.) 
SIR — The screw and spring-press which I have the 
honour to present to the inspection and for the approba 
tion of the Society for the Encouragement of Arts, &c. 
will, I trust, be found in a superior degree adapteil to 
* Tilloch, vol. 21, p. 249. From the Transactions of the Society for the En- 
couragement of Arts , &c. vol. xxi. — A bounty of ten guineas was voted to the au - 
thor by the Society. 
