NATURE 
[ApRIL 4, 1907 
) 
548 
of compressions. Considering, then, gas and petrol 
engines as air engines, the theory is very simple. There 
are three symmetrical cycles of compression air engines. 
It is interesting to note that for equal compressions it 
does not matter whether Carnot cycle, constant volume, 
or constant pressure engines be used—the theoretical 
efficiency is the same. It has been found in practice that 
a first-class modern engine operating on the constant- 
volume cycle will give in indicated power 0-7 of the heat 
which a perfect air engine would give under the same 
conditions of compression, proportions, &c. Thus an 
engine having an air-engine efficiency of o-5 will give 
indicated work 0-5 X0-7=0-35, of all the heat given to it. 
The air standard has proved its utility as a guide to 
the engineer for twenty-five years now, and has been 
adopted by a committee appointed by the Institution of 
Civil Engineers on the standards of efficiency in internal- 
combustion engines. To enable further progress to be 
made, however, it is now necessary to know more of the 
actual properties of the working fluid. 
The earlier experiments made by the lecturer, and sub- 
sequent experiments made by Oliver in America, and by 
Messrs. Bairstow and Alexander in this country, were only 
in strictness applicable to the behaviour of highly heated 
gases ina closed vessel. No means of obtaining a cooling 
curve in an engine cylinder had been proposed. 
At the beginning of 1905 the lecturer designed a new 
method, and made a considerable number of experiments 
on a 50-horse-power gas engine. By altering the valve 
arrangements of the engine so that when desired both inlet 
charge valve and exhaust valve can be held closed, 
diagrams were obtained from which a cooling curve was 
calculated. 
In this method no gases are allowed to exhaust from 
the cylinder. The piston accordingly compresses the whole 
contents into the compression space, and the temperature 
which has fallen by expansion rises by compression. A 
point is touched on a vertical line from the end of the 
card. On expanding, a line below the first compression 
line is traced, then another compression line is obtained, 
and so on; a series of compression and expansion lines 
is obtained, each terminating under compression at 
certain specific points. 
In this way a cooling curve is obtained which shows 
the real temperature drop upon the expanding and com- 
pressing lines. From this curve, by somewhat trouble- 
some calculations, the mean apparent specific heat of the 
charge can be obtained for each expanding line. A curve 
of specific heats so obtained was shown. 
These numbers give a very fair indication of the heat 
loss incurred in the cylinder, and the cooling curves show 
that for the whole stroke the mean temperature of the 
whole enclosing walls is about 70° C. when the water- 
jacket is cold and about 200° C. when the water-iacket is 
hot, but for the inner part of the stroke, the first three- 
tenths of the stroke, the mean temperature is much higher 
—170° C. when cold and 4oo° C. when hot. 
This method of investigation gives a more accurate 
knowledge of the properties of the working fluid, so far 
as the thermodynamics of the engine are concerned, and it 
enables us to make an entire heat balance-sheet from the 
diagram only. Full-load diagrams taken from the engine 
have been examined by this method, and account for 105 
thermal units, when the calorimeter shows 106 thermal 
units to be present. The method appears capable of very 
considerable accuracy. 
Prof. Hopkinson has attacked the problem of heat loss 
to the closed vessel by another method, using a calori- 
meter by which the heat leaving the hot gases at any time 
is measured electrically, while at the same time the pressure 
is indicated. This arrangement promises to give important 
information as to the rate of loss in gaseous explosions, 
from which observations some deductions may be drawn 
as to specific heat and as to time of termination of com- 
bustion. 
The lecturer is continuing investigations on various sizes 
of engines with a new form of optical indicator. An 
indicator card taken with this instrument was shown. 
The appearance of this indicator card is most interesting. 
There is slight discontinuity in the rising line, and just 
as maximum pressure is approached the indicator begins 
NO. 1953, VOL. 75] 
to oscillate rapidly through a small distance. These 
oscillations continue all down the explosion stroke, die 
out gradually, and do not terminate until the end of the 
compression stroke. The period of the oscillations is about 
600 per second; the amplitude gradually decreases until it 
has practically ceased at the end of the first compression. 
The period of the indicator is about 200 to the second, 
so far as ordinary piston displacement is concerned. From 
this it follows that considerable pressure disturbances 
within the cylinder must have occasioned the oscillation. 
In this particular engine, the explosion is always accom- 
panied by a peculiar whistling sound, which seems to 
start just about the time the diagrams show the beginning 
of the oscillations, that is, immediately after ignition. It 
is somewhat difficult to account for this peculiar action, 
but it appears to have some connection with the discon- 
tinuous nature of combustion of a mixture of inflammable 
gas or vapour with air. This was illustrated by an experi- 
ment in which inflammable mixture was ignited at the 
open end of a long tube. The flame travels back along the 
tube, accompanied at first by a low, roaring sound, which 
increases in intensity as the end of the tube is reached, 
terminating in a loud snap. When this occurs, the flame 
flashes back again, and there is obvious oscillation of 
some kind proceeding. It is not known why the mixture 
flame burns in this way, but this particular roaring or 
whistling seems to occur only when combustion is going 
on, and is noticed in all pressure flames in the open air. 
It appears highly probable, then, that wherever this oscil- 
lation goes on combustion is still proceeding. 
Experiments have also been made by Messrs. Holborn 
and Austen on the specific heat of air and carbonic acid 
by an entirely different method, and there is reason to 
hope that as a result of experiments which are progressing 
in this country and on the Continent the whole question 
will be cleared up in the next few years in a satisfactory 
manner. 
As one who has given thirty years’ study to the prac- 
tical and scientific problems involved in this matter, it is 
exceedingly gratifying to find a great and increasing interest 
in the subject which will lead to the complete investi- 
gation of the complex properties of the working fluid. 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
Dr. W. Peppie, lecturer in natural philosophy in the 
University of Edinburgh, has been appointed to the Harris 
chair of physics in University College, Dundee, in 
succession to Prof. Kuenen. 
Pror. Mratt, F.R.S., who was appointed professor of 
biology in the Yorkshire College of Science in 1876, is 
retiring from his chair in the University of Leeds at the 
end of the present session. We understand that the council 
has decided to establish separate chairs of zoology and 
botany, and will shortly proceed to appoint professors of 
these subjects. \ 
THE province of Saskatchewan is only eighteen months 
old, but already (says the Times) it is devoting its re- 
sources to the establishment of a State university. A Bill 
just introduced by the Provincial Government in the Legis- 
lative Assembly at Regina provides for the incorporation 
of such a university under a chancellor, convocation, 
senate, board of governors, and council. The number and 
nature of the faculties to be established will be decided 
by the university senate. The maintenance of the uni- 
versity is to be provided out of the general revenues of 
the province and also by a percentage of the net receipts 
of the province under the Succession Duties Ordinance. 
THERE has been serious divergence of opinion for more 
than two years as to the policy of the Marine Biological 
Association of the West of Scotland. This association was 
founded in order, according to the first article of its con- 
stitution, to investigate the marine fauna and flora of 
the Clyde sea area, to maintain a biological station at 
Millport or other suitable locality, and generally to foster 
and encourage biological research. At the annual meeting 
of the association on March 27 an amendment was carried 
by a majority of one vote ‘‘ that while approving generally 
