Moveable-Derrick Crane. 63 
little, by applying a tackle-fall to the material in suspension, 
and dragging it by main force from the perpendicular to the 
place required, or as near to it as could possibly be effected. 
From this and the other defects, it will be admitted, that 
the gibbet-crane was a very imperfect machine for lifting 
and conveying heavy masses of building, or other material, 
to or from their ever-varying positions ; and required to be 
taken down and removed, in most cases, every other day,— 
thereby incurring great expense and loss of time. 
By a reference to the small figure of the improved move- 
able-derrick crane, fig. 3, B (C D being a cross section of a 
part of Granton Pier), the inefficiency of the common or gib- 
bet crane for executing such work. profitably, compared with 
the moveable-derrick crane, will be quite obvious; and 
shews that some other machine was desirable, possessing 
greater economy and despatch for depositing the blocks of 
stone over the whole range of these immense slopes. 
On entering with my partners into the contract with His 
Grace the Duke of Buccleuch for the erection of Granton 
Pier, the deficiency of the common crane called my attention 
to various schemes for a remedy, which at last resulted in 
the construction of the improved moveable-derrick crane, a 
working model of which is now before you. (Plate IL, figs. 1 
and 2.) 
It may be proper, however, here to state, that, although I 
never had then either seen or heard of anything of the kind, a 
crane having a moveable-jib, but with very different and more 
complicated machinery than mine, was used by Mr Steven- 
son at the Bell-Rock Lighthouse, upwards of thirty years 
since: the defects of which, as well as the improvements ef- 
fected by me, were very clearly pointed out in a paper read 
before the Society some time since, by Mr James Slight, 
F.R.S.S.A., engineer, Edinburgh, containing an exposition of 
the strains to which cranes of various forms are subject ;— 
for which the honorary medal was awarded to him. 
I am sorry to occupy the time of the Society with a mere 
_ detail of circumstances ; but I wish to state, as a proof of the 
extent of existing prejudices against the introduction of 
many useful improvements, that, after I had, at a great ex- 
