532 
POPULAR SCIENCE REVIEW. 
surface condensation, — that is, the steam to he condensed passes through a 
long and tortuous series of tubes, which are refrigerated by a constant 
flow of cold sea- water made to circulate by pumps worked by the engine ; 
the great object of surface condensation being to leave the condensed 
steam free of any intermixture with the salt-water. The mechanical 
arrangement adopted by Messrs. Jack & Co. is curious. The framing of the 
engines is entirely tubular, and the condensers occupy the spaces between 
the plates that form the walls of the frames ; this affords space within 
the latter for an immense extension of condensing tubes, and also for the 
use of a proportionately large quantity of sea-water as a refrigerant. 
Another feature is the “ feed- water heater,” by means of which the 
exhaust steam is made to part with its heat to the condensed steam which 
feeds the boiler, entering the latter at a high temperature. We need not 
inform our practical readers that the great problem of the day in marine 
engineering is the economy of fuel, and the consequent increase of the 
distance that a steam-vessel can run without coaling, and Messrs. 
Jack & Co. seem to have achieved an important step in that direction. The 
working of the model was admirably explained by a gentleman connected 
with Messrs. Jack & Co.’s establishment, and seemed to give great satis- 
faction. Some surprise was expressed that the Imperial Government 
should have preceded the English Admiralty in putting to a practical test 
the asserted advantages of this form of engines for screw men-of-war ; but 
British inventors and manufacturers know too well that private firms are 
held in little honour in their own country, or at any rate by their own 
Government. Y. 
Paris, June , 1868. 
FALSE MOONS, OR PARASELENJE. 
As the occurrence of paraselense, or false moons, is rare in these 
latitudes, I send a short account of the appearances which presented 
themselves to the inhabitants of this small town and its neighbour- 
hood on the night of May 29th, 1863. I find no mention of the 
phenomenon in the local papers of this day (June 6th), or in the London 
papers of the week past, and imagine therefore that it was seen by com- 
paratively few. The day had been hot, with a W.N. VV. wind bearing dark, 
heavy masses of cumulus. In the evening the moon was bright, but 
slightly veiled by a thin layer of misty cloud. At about 9.40 p.m. two 
false moons of great brilliancy appeared east and west of the true moon ; 
they showed prismatic colours, and each was adorned with a comet-like 
tail stretching outwards. They were united by a circular halo of about 
40° diameter, the upper arc of which was very distinct and beautiful. At 
about eleven o’clock a smaller halo very finely coloured encircled the 
moon; it had a diameter about three times that of the moon itself. These 
interesting phenomena continued visible with varying brilliancy until 
midnight. 
I send a diagram of these appearances to help out my faulty description. 
Thomas Edwd. Amyot. 
Diss, Norfolk, June 6th, 1863. 
