4 
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August 13, 1885} 
NATORE 
345 
regulate the speed finally. But where perfect steadiness 
is desired it is probably better not to cut off much before 
half stroke, especially if a single-cylinder engine is used. 
The use of accumulators as regulators would of course 
prevent a great deal of the fluctuation, and would permit 
of the steam being cut off much earlier without causing 
any apparent unsteadiness in the light. 
The electric governor was fixed on the engine and 
worked for the first time on January 13 last. The im- 
provement was remarkable, the lights remaining steady, 
without the sudden alternations of brightness and dulness 
which had occurred before. But it was still found that 
with any considerable variation of boiler pressure or of 
load the electromotive force in the mains varied more 
than was thought conducive to long life in the lamps. 
As however it was found that, by augmenting or diminish- 
ing the weight suspended from the core bars, the electro- 
motive force could be brought back to its normal amount, 
it occurred to the author to fix an upright cylinder in 
direct communication with the boiler, and to make its 
piston-rod press upwards on the core-bars: the diameter 
of the cylinder being experimentally determined by ob- 
serving the weight necessary to be added or removed for 
certain variations in boiler pressure. This arrangement 
caused a very great improvement; and when the load 
was approximately the same it maintained the electro- 
motive force constant under very considerable variation 
of steam pressure. When, however, the load was varied 
very considerably, say from one lamp to a hundred, it 
was found that more variation took place in the electro- 
motive force than was desirable. 
The arrangement was accordingly modified by causing 
the piston-rod to act upon a lever, and by introducing a 
second cylinder supplied with steam from the steam-chest, 
the second piston-rod acting not upon the same lever but 
upon the other side of the fulcrum. The end of the lever 
was furnished with a steel knife-edge, bearing against 
another knife-edge set at right angles to it upon the pro- 
longation of the core-bars. The cylinders were also both 
of them made larger, and were placed so that they could 
either of them be moved nearer to or further from the 
fulcrum of the lever, whereby the resultant effect of their 
differential power could be easily adjusted. This arrange- 
ment answered very well indeed, and it was found that 
the lights could be varied from 1 to 100 and the boiler 
pressure from 30 lbs. to 60 lbs. with but very slight varia- 
tion of electromotive force in the mains: provided of 
course there was sufficient steam to do the work required. 
It is also quite easy to cause the electromotive force to 
rise as the load on the engine increasss—or in other 
werds as more current passes through the main—by 
simply giving greater leverage to the piston connected 
with the steam-chest. In fact with this arrangement the 
electromotive force can be maintained practically con- 
stant, or can be made to vary in any desired manner with 
variations of steam pressure or of load. 
Several experiments were made by Mr. Richardson 
and the author on the action of this regulator, the results 
of which were as follows :—When the load on the engine 
was allowed to remain constant, with only one lamp 
alight, it was found that while the steam pressure was 
allowed to vary between 31 Ibs. and 55 lbs., the electro- 
motive force remained constant at 90 volts. Afterwards, 
with the same extent of variation in steam pressure, and 
with the load also varying from 1 lamp to 91 lamps, the 
electromotive force varied only 2 volts—from 91 volts to 
93 volts. The introduction of this governor has, in the 
author’s opinion, contributed very largely to the duration 
of the lamps also. The discussion of this paper, which 
was very full, was mainly upon the governor described and 
the governing of engines for electric work, the necessity 
of an electric governor being maintained on the one side, 
whilst on the other it was held that all that was required 
was an ordinary mechanical governor of great sensibility. 
The Rev. E. Venables, at the conclusion of the discussion, 
invited electrical engineers to advise the Cathedral authori- 
ties, as they should like to see, as a practical result of the 
visit of the Institution of Mechanical Engineers to Lincoln, 
the lighting of Lincoln Cathedral by electricity. 
A VOLTAIC CELE WITH A SOLID 
ELECTROLYTE 
BELIEVE that there has never hitherto been made a 
voltaic cell with a solid electrolyte which was capable 
of generating the smallest sensible current—at least at 
ordinary temperatures. Sir William Thomson found that 
when warm glass was placed between plates of zinc and 
copper, the existence of an electromotive force was indi- 
cated by an electrometer in connection with the metals, 
and Profs. Ayrton and Perry extended the observation to 
the cases of paraffin-wax, gutta-percha, indiarubber, and 
shellac. But it is needless to say that with electrolytes 
of such enormous resistance no current could be generated 
of sufficient strength to be detected by any galvanometer, 
however delicate. 
On June 27 I exhibited to the Physical Society a little 
cell consisting of plates of silver and copper, between 
which was contained a mixture of 1 part of copper-sulphide 
with 5 of sulphur. When this cell was connected with a 
reflecting galvanometer it produced a current by which 
the spot of light was at once deflected off the scale, 
copper being the positive pole. ‘The electromotive force 
was found to be ‘o7 volt, and the internal resistance 6537 
ohms. The current, therefore, though far more than merely 
sensible, was small. Attempts were made to reduce the 
internal resistance by diminishing the proportion of sulphur 
contained in the mixture, but it appeared that as the sulphur 
was diminished the electromotive force was also dimin- 
ished, until, when there was no free sulphur at all, the 
cell failed to produce the smallest measurable current. 
It occurred to me that the sulphur owed its efficacy to 
the fact that it formed a film of silver sulphide upon the 
surface of the silver plate by direct combination. I there- 
fore made a cell thus :—A thin layer of copper sulphide was 
spread upon a copper plate and compressed into a compact 
mass against a surface of polished steel. A layer of silver 
sulphide was then spread upon the copper sulphide, and 
the cell was completed by pressing a silver plate upon 
the silver sulphide. The current which this cell produced 
through the shunted galvanometer was considerably 
stronger than that generated by the cell first described ; 
but still the result was not quite satisfactory, and there 
seemed to be indications of short-circuiting, which I 
thought might possibly be due to the penetration of 
particles of copper sulphide through the layer of silver 
sulphide. The silver plate was therefore removed from 
the cell, and, having been brushed over with a weak 
solution of sulphur in bisulphide of carbon, it was heated 
over a gas flame, and soon became covered with a uni- 
form and continuous coating of sulphide. The heating 
was continued until all the free sulphur was evaporated. 
When the cell was reconstructed with this prepared plate 
it produced a current of 6800 micro-amperes through an 
external resistance of °2 ohm, and was able to deflect the 
pivoted needle of an ordinary coarse galvanometer. 
The dimensions of the cell are as follows :—The copper 
and silver plates measure 24 inches by 2 inches; the 
thickness of the two layers of sulphide (strongly com- 
pressed) is about 1-20th inch ; the E.M.F. is ‘053 volt, and 
the internal resistance is therefore about 7 ohms. 
This cell seems to be exactly analogous in its action to 
a Daniell cellin which plates of copper and zinc are im- 
mersed in solutions of copper sulphate and zinc sulphate. 
Silver is probably the best (or only) possible metal for the 
positive plate, but some other metal might perhaps be 
substituted for the copper with advantage. 
SHELFORD BIDWELL 
