Oct. 28, 1886] 
route, returning by New Zealand, Samoa, the Sandwich 
Islands, San Francisco, and New York. The observa- 
tions relate principally to barometrical heights, tempera- 
ture of air and sea, moisture of the atmosphere, and twi- 
light phenomena, including zodiacal light, whilst passing 
through the Red Sea and tropical portions of the Indian 
and Pacific Oceans. 
Although in previous yearly Reports Dr. Neumayer has 
published much information respecting the internal work- 
ing, aims, and results of the Observatory he so ably 
directs, it is only from the perusal of this seventh Report 
that a full idea of the pains which Germany has taken on 
behalf of her sea-going population, in building and 
equipping at considerable expense the noble Naval 
Observatory at Hamburg, can be obtained. It should 
also be remembered that there are several minor affiliated 
institutions in Germany of like intent. 
THE INSTITUTION OF MECHANICAL 
ENGINEERS 
Ae the recent meeting of the Institution of Mechanical 
Engineers, held in Leeds under the presidency of 
Mr. Jeremiah Head, a paper was read “ On Triple-Ex- 
pansion Marine Engines,’ by the late Mr. Robert 
Wyllie of Hartlepool. During the last few years the 
high-pressure triple-expansion engine has proved the 
successful rival of the double-expansion compound, and 
the object of the paper was to bring forward the results 
of recent experience with this new type of engine, and to 
consider briefly the various points which have a direct 
bearing on its efficiency, as well as the most suitable 
design for marine purposes. The general conditions of 
efficiency were stated to depend on the approximate 
equality in the range of temperature in each cylinder, 
in the initial stress on each crank, and in the indicated 
horse-power of each engine. As complementary to these 
are steam-jacketed cylinders and other matters which 
are first treated of. As regards steam-jackets, when in 
triple-expansion engines attention is paid to the equal 
division of the total range of temperature amongst the 
cylinders in which the successive stages of expansion 
take place, the benefits arising from the use of steam- 
jackets are naturally not so great as in single-cylinder 
engines with a high rate of expansion ; but however care- 
fully the triple engine may be designed, the jacketing of 
at least the intermediate and low-pressure cylinders is 
essential to maximum efficiency. The ratio of the 
cylinder capacities depends on the pressure of the steam 
and type of engine, the high-pressure cylinder being larger 
in proportion where large range of power and economy of 
fuel is not so important, as in war-ships as compared with 
cargo steamers. To obtain even approximate equality in 
powers, temperatures, and stresses requires the greatest 
care in designing the steam-passages throughout the 
engine, so that the velocities of the steam at the various 
points and the degrees of cut-off by the valves may be 
carefully proportioned. Too much care cannot be taken 
in the design of the steam-ports and exhaust-passages of 
the low-pressure cylinder. The ports should be as small 
as possible to reduce the clearance to a minimum, and 
the speed of the entering steam should not be so high as 
to cause excessive frictional resistance, nor that of the 
exhaust so high as to augment the back-pressure, and 
consequently the greatest efficiency is obtained when the 
revolutions and indicated horse-power are not required 
to vary to any great extent. Contracted or indirect 
exhaust-passages in the high-pressure and intermediate 
cylinders have the effect of causing a larger difference 
between the back-pressure on one piston and the initial 
pressure on the next, thus diminishing the efficiency of the 
steam. The cut-off necessary for the highest efficiency is 
governed to a great extent by the speed of the entering 
steam and the nature of the passages. In the interme- 
NATURE 
625 
diate and low-pressure cylinders, too high a velocity of 
the entering steam will produce excessive frictional re- 
sistance, causing adrop in the expansion-curve, as well 
as unduly high receiver-pressure, thus disturbing the 
equality of temperatures and of initial stresses. Some 
diversity of opinion has existed as to the order of 
sequence for the three cranks. The author considered 
the best sequence to be the high-pressure leading, low- 
pressure following, and intermediate last. As regards 
the number of cranks, the best design is to have two 
cylinders on each crank for a two crank engine on the 
triple-expansion system, as it is then possible to get an 
approximately equal initial stress on each crank, the 
arrangement necessitating one of the three stages of ex- 
pansion taking place in two cylinders instead of in one. 
A marine engine should be so designed that any working 
part can be easily examined or removed, the arrangement 
of cylinders on three cranks fulfilling the required con- 
ditions more nearly than any other design. The require- 
ments of a good valve-gear are, that it shall give at both 
ends of the cylinder an equal distribution of steam at all 
grades of expansion, with a minimum of working parts 
and no undue strains. The four principal methods are : 
by the single eccentric, by the double eccentric, by 
taking the motion from the connecting-rod, and by a com- 
pound motion derived from both the piston-rod and the 
connecting-rod ; all have their advantages and defects, 
and vary considerably in complexity and multiplicity of 
parts. A comparison of practical results with compound- 
and triple-expansion engines is in favour of the latter, as 
regards dead-weight carried, speed, indicated horse-power, 
and coal-consumption, the latter being so lowas 1°41 lbs. per 
h.p. per hour, proving this class of engine to be most effi- 
cient. The paper concluded with a reference to artificial 
draught for boilers, in the special arrangement described 
the air being heated both inside and outside the uptake, 
balanced fire doors being applied, which on being opened 
shut off automatically the hot air supplied by the fan 
both above and below the fire-bars. 
An important discussion followed the reading of the 
paper. Mr. Wm. Parker, of Lloyd’s, looked upon the 
triple-expansion engine as the engine of the future. Profs. 
Kennedy and Smith drew attention to the high initial 
pressures employed in the triple engine, 150 lbs. per 
square inch as compared with 75 lbs. per square inch in 
the compound engines being the cause of their higher 
efficiency ; and other speakers having drawn attention to 
special features in the designs, the further discussion of the 
paper was put off to the spring meeting of the Institute. 
Afterwards the President, by request, declared the 
Leeds Engineering School of the Yorkshire College open, 
and spoke in hopeful terms of the useful work it had 
doubtless before it. 
NOTES 
WE regret to have to announce the death last week of Dr. 
Guthrie, Professor of Physics at the Normal School of Science. 
WE understand that the Jardin des Plantes has acquired 
for its botanical collections the herbarium of Lamarck. We 
do not know under what circumstances this had travelled so 
fax from France. But until recently it was the property of Dr. 
Roeper, Professor of Botany in the University of Rostock. He 
incorporated it with his own herbarium, and the whole was 
purchased at his death by the University for 21,000 marks 
(1050/.). Lamarck’s plants have however been separated, and 
as we understand purchased by the French Government. 
Tue front and sides of the new building for the galleries of 
natural history in the Jardin des Plantes are now nearly com- 
plete. But it will be two years or nearly so before the interior 
and the fittings can be finished. The collections will then be 
moyed into the new portion, and the present galleries rebuilt to 
form the back of the square. The hollow interior will be covered 
