:, TRANSACTIONS OF THE SECTIONS. 129 
known. It is difficult to estimate the amount of friction beforehand; but supposing 
it to be ‘a little greater in proportion than that of a Cornish pumping-engine, the 
author calculated that about 25,000 cubic feet of air per hour may be cooled down 
from 90° Fahr. to 60° by an engine of 1-horse power *. 
EA tt 
A Model of a new Reaping Machine, by Mr. R. Robinson, was exhibited by one of 
the Secretaries. 

Design for Safety Harbours. By Captain J. SAUNDERS. 
The advantages sought by the author are, durability, cheapness of execution (when 
compared with the important object it has in view), and security from damage during 
the progress of the work. The sea pavement, which has heretofore been the ruin of 
_ our best harbours, will be by this design dispensed with, substituting a strong sea-wall 
instead. ‘The bell-work to seaward will be constructed on a new plan, diminishing 
one foot in each course till it reaches low-water mark, on which the great sea-wall will 
commence; this wall will be supported from the interior by horizontal arches and 
sectional walls; the horizontal arches will be filled with concrete and small stones to 
high-water mark. The contractor may undertake, with a small capital, a large work 
without any risk or danger, as each section can be completed before another is com- 
menced, as particularly described on the design and model; the cost of execution will 
be less, and the permanency greater, than by the usual mode of construction, and the 
design may be adapted to any situation or scale of magnitude. 
On the Natural Peculiarities and Advantages of the Mineral Field and the 
proposed Harbour of Fair Head. By W.H. Smitu. 
This was a proposal to erect a harbour at Fair Head, the extreme point on the 
north-eastern coast of Ireland, and establish a submarine telegraph between it and 
the Mull of Cantyre, which is only twelve miles distant on the Scottish coast, and is 
the principal point to Glasgow. Having pointed out the variety of mineral wealth 
and natural products, consisting of coal, iron, sulphur, copperas, ochre, building- 
stone and limestone, and other valuable substances which abounded in the district, but 
_ could not be turned to full advantage in consequence of the want of a harbour,—while 
_ shipwrecks on the coast have occurred annually since the old harbour of Ballycastle 
adjoining was allowed to fall to decay,—the paper stated, that a harbour at Fair Head 
_ would be a permanent protection to shipping, and besides increasing the spirit of com- 
‘mercial enterprise, would in some cases be the means of shortening the passage to 
America by several days. The harbour was proposed to be constructed on the recoil 
principle, being formed of a framework fastened to piles, with counterbalancing weights 
attached, so that it would yield to the waves and yet recover its position continually. 
A lighthouse on the same principle was proposed to be attached. 

















= ee 
On Penrose and Bennett's Sliding Helicograph. 
Communicated by Professor C. Prazzi SMYTH. 
The author, Mr. Penrose, observed, ‘‘ I was led, during my researches on the subject 
of the refined curves of the Greek mouldings and ornaments, to consider whether it 
would be possible to contrive some method of describing the volutes and scroll-work at 
once more ready and more satisfactory than the tiresome approximations, by means of 
circular ones, which have generally been used. 1 invented an instrument for this pur- 
* From calculations made since this paper was read, it appears that if the compressing 
pump and expansion cylinder be made on the principle of the gasometer (by bells dipping 
into a tank of water, as in M. Struyé’s machine for extracting the foul air from mines), the 
power required to reduce the temperature of a cubic foot of air from 90° Fahr. down to 60°, 
will be about 164 foot-pounds for the mere reduction of temperature, and about 134 foot- 
pounds additional for friction, or 30 foot-pounds in all; so that by an engine of one real 
horse-power, 66,000 cubic feet of air per hour may be cooled from 90° to 60° Fahr., being 
enough for the supply of 264 persons, at 250 cubic feet per hour each. 
1852. 9 
