44 
NATURE 
| NovEMBER 12, 1896 
Bay, coloured from life. A few were also hung in each room. 
In the tank-room were various nets (surface, large mid-water and 
bottom), circular flounder-nets, mussel and other dredges, mussel 
and cockle implements, Italian eel-spear, hand-nets, scoops, 
water-telescope, thermometers (surface, deep-sea, and open-air), 
sieves, and various models of trawls, crab pots, &c. In the 
Director's room were the multitudes of preparations connected 
with the life-histories of the, food fishes, rare pelagic forms, 
such as the larval Polygordius, Mitraria, Tornaria, and the 
wonderful larva of Zzdza. In the specimen-room were the 
type-series of the pelagic fauna of the Bay from January to 
December, an extensive collection of pelagic ova of fishes from 
various parts of the eastern and western shores of Scotland, a 
series of preparations connected with the life-history of the 
salmon, a reference-collection of invertebrates, including an in- 
teresting series of the mussels of the Eden, oysters from the 
Forth and from Whitstable, a series of fishes, and other 
preparations. 
THE INSTI1UTION OF MECHANICAL 
ENGINEERS. 
@* the evenings of Wednesday and Thursday of last week, 
the 4th and 5th inst., an ordinary general meeting of the 
Institution of Mechanical Engineers was held in London, the 
theatre of the Institution of Civil Engineers having been lent 
for the purpose. The President, Mr. E. Windsor Richards, 
occupied the chair on both evenings. 
There were three papers set down for reading, as follows :— 
“* Research Committee on the Value of the Steam-Jacket ; | 
Experiment on a Locomotive Engine,” by Prof. T. Hudson 
Beare and Mr. Bryan Donkin. 
“Transmission of Heat from Surface Condensation through 
Metal Cylinders,” by Lieut.-Colonel English and Mr. Bryan 
Donkin. 
“Breakdowns of Stationary Steam-Engines,” by Mr. Michael | 
Longridge, of Manchester. 
The two first papers were taken on Wednesday, Thursday 
evening being devoted to Mr, Longridge’s memoir. 
The Research Committee on the Value of the Steam-Jacket 
has been in existence for a long time now, and has proved one of 
the least, if not actually the least satisfactory of all the research 
committees constituted by the Council of the Institution. Most 
of these committees have done admirable work, and added 
largely to the stock of professional knowledge and accumulated 
data which engineers have todraw. Steam-jacketing is perhaps 
the most abstruse question which has been made the subject of 
an inquiry, comprising, as it does, problems extending beyond 
engineering proper far into the province of physical science. 
Nevertheless, in the present day of enlightenment, with the 
professor so widely abroad, more ought to have been done than 
has been done by this committee. It would be difficult to 
select an engine more unfitted for making an_ inquiry 
upon as to the value of the steam-jacket than an ordinary 
locomotive. Its rapid piston speed—or, rather, the high 
rate of turning—alone is sufficient to render it unsuitable for this 
inquiry ; but, in any case, a locomotive is the most difficult 
engine from which to obtain experimental data. It is an 
athletic feat of no mean order to take even indicator diagrams, 
when one has to hang on to the side of an engine travelling at 
a speed varying from anything up to sixty, or perhaps eighty 
miles an hour. Then a locomotive, even with constant train 
load—a condition which can hardly be ensured in ordinary 
work—is seldom for five minutes at a time exerting the same 
power, owing to varying gradient, state of the rails, and force or 
direction of wind—the latter a most important consideration. 
Steam may be shut completely off when descending asteep bank, 
or the regulator may be full open and link in the last notch 
under exactly opposite conditions. Between these two states 
we have all grades of linking-up, an operation which so affects 
the distribution of steam—compression, expansion, &c.—that 
one would think the steam-jacket would finally give its job up in 
disgust from fair despair of knowing what it should do. 
The result of all this is shown in the report, which possesses 
the merit of being absolutely honest and straightforward. Four 
trial runs were made between Manchester and York during 
ordinary working, with its attendant stoppages and delays. The 
Steam-jacket fitted was of a temporary nature, and the method 
of testing was to make one run each way with the jackets in 
NO. I411, VOL. 55] 
steam, and a like number of runs with the jackets empty. Coal 
was weighed and feed-water measured by a Siemens’ meter. 
Mr. Michael Longridge drew off samples of chimney gases 
for analysis. Jacket-water was also drawn off and measured. 
Speed was taken by a Boyer recorder, and the revolutions 
assumed from its records. 
In spite of the fact that we know nothing niore about the value 
of the steam-jacket than we did before the experiments were 
made, the trials added, as a by-product, something to the know- 
ledge of railway engineers on the performance of the locomotive ; 
but, in any case, the thanks of the Institution are due to the 
authors of the paper for their disinterested labours. 
The second paper was a complement to the first ; for the 
rate of transmission of heat to and through metal is the chier 
thing necessary to be known for determining the value or 
steam-jacketing of engine cylinders. The problem is a vexed 
one, and no inquiry yet made has taken us beyond its 
threshold. The authors have attacked the subject by an en- 
deavour to ascertain the actual temperature in the interior of 
the metal, and by observing the exact appearance of the film 
of water deposited, and, further, by determining whether such 
a phenomenon as cloudy steam really exists. Their apparatus 
consisted of a strong vertical glass cylinder about 52 inches 
in diameter and 2} inches high. Inside this was placed a 
metallic cylinder. The annular space between the glass cylinder 
and the enclosed metallic cylinder was filled with steam, whilst 
through the interior of the metal cylinder an ascending stream 
of cooling water was made to circulate. In order to deter- 
mine the thermal gradients in the metal, when its thickness 
allowed of so doing, the temperatures of the interior were 
taken in vertical holes 1/8 or 1/16 of an inch in diameter, 
drilled at different distances from the condensing surfaces, and 
filled with mercury, into which slender thermometers were 
inserted. Illustrations of the apparatus were hung on the 
walls of the theatre, and will be reproduced in the published 
volume of the Zyansactzons of the Institution. The pressure 
of steam, volume and temperature, of circulating water, and 
other trial conditions were controlled by suitable apparatus. 
The first result arrived at was that the authors consider it was 
not possible to trace the slightest appearance of cloudiness or 
mist, or of water suspended in the body of the condensing 
steam. The water of condensation was deposited on the 
surfaces. A reproduction was given of a photograph of the 
film of water on the surface of smooth cast-iron as it appeared 
through the glass cylinder, the steam pressure being 20 Ibs. per 
square inch, and the rate of condensation somewhat slow. 
The velocity of circulating water varied between 0°032 and 
0°415 feet per second. The different metallic cylinders tried 
| were made from cast-iron with both rough and smooth surfaces 
11/32 and 31/32 of an inch thick,-:copper, and brass with smooth 
surfaces 2/32 of an inch thick, and smooth steel 1/32 and 10/32 
of an inch thick. The rate of heat transmission was found 
by observing the rise of temperature in a known quantity of 
circulating water, and by noting the weight of steam 
condensed. Corrections were made to allow of accidental 
losses. Without publishing the diagrams on which the results of 
the experiments were plotted, it would be impossible to give 
details of the observed results unless we printed the voluminous 
tables attached to the papers. The greatest quantity of heat 
transmitted per second was about thirty-five thermal units, and 
the least seven thermal units per square foot of internal surface 
of cylinder. The authors consider that the film of water 
deposited by condensation, and adherent to a metallic surface, 
resists the transmission of heat in exactly the same way as an 
equivalent greater thickness of metal would do. The thick- 
ness of the water films, as determined by the difference of 
temperature, is less on a smooth surface of cast-iron than ona 
rough one, and is apparently not affected by the admission of 
steam-jets to sweep the surfaces. There is, the paper says, no 
apparent difference in the resistance to transmission of heat 
between the surface-layer of metal and the next to it; or, in 
other words, there is no drop in temperature on entering or 
leaving the metal. The thermal gradient at any point in the 
metal would be uniform in a flat plate, and becomes steeper 
towards the interior of a hollow cylinder as the circumference 
diminishes. At any point on the surface of the metal next to 
the circulating water, the temperature, owing to an adherent 
film in which the thermal gradient exists, is much in excess of the 
mean temperature of the circulating water at the same point. 
In the discussion which followed the reading of this paper, 
