[Illustration: IMPROVED AIR REFRIGERATING MACHINE.]

Messrs. J. & E. Hall, Dartford, exhibit at the International Health
Exhibition, London, in connection with a cold storage room, two sizes
of Ellis' patent air refrigerator, the larger one capable of
delivering 5,000 cubic feet of cold air per hour, when running at a
speed of 150 revolutions per minute; and the smaller one 2,000 cubic
feet of cold air per hour, at 225 revolutions per minute. The special
features in these machines are the arrangement of parts, by which
great compactness is secured, and the adoption of flat slides for the
compressor, instead of the ordinary beat valves, which permits of a
high rate of revolution without the objectionable noise which is
caused by clacks beating on their seats. The engraving shows the
general arrangement of the apparatus. Figs. 1 to 4 show details of the
compression and expansion valves, which are ordinary flat slides,
partly balanced, and held up to their faces by strong springs from
behind. The steam, compression, and expansion cylinders are severally
bolted to the end of a strong frame, which though attached to the
cooler box does not form part of it, the object being to meet the
strains between the cylinders and shaft in as direct a manner as
possible without allowing them to act on the cooler casting. Each
cylinder is double acting, the pistons being coupled to the shaft by
three connecting rods, the two outer ones working upon crank pins
fixed to overhung disks, and the center one on a crank formed in the
shaft. The slide valves for all the cylinders are driven from two
weigh shafts, the main valve shaft being actuated by a follow crank,
and the expansion and cut off valves from the crosshead pin of the
compressor. The machines may be used either in the vertical position
as exhibited, or may be fixed horizontally; and it is stated that the
construction is such as to admit of speeds of 200 and 300 revolutions