OcTOBER 29, 1897. ] 
its test if appeared that the transformer 
agreed in resistance, regulation and effi- 
ciency almost exactly with the values com- 
puted in advance. The fall in E. M. F. be- 
tween no load and full load was 2.3 per cent., 
and the efficiency at full load was 95.4 per 
eent. This paper is published in the Hlec- 
trical World for September 18, 1897. Dr. 
Karl E. Guthe described some experi- 
ments on the electrolytic action of con- 
densers. He used commercial condensers, 
and found polarization and recovery much | 
as in an electrolytic cell. He showed sev- 
eral curves illustrating the results obtained. 
The graphical treatment of alternating 
currents in branch circuits in cases of vari- 
able frequency, by Professor H. T. Eddy, 
was a very full exposition of the subject. 
Many diagrams were shown, in which a 
whole series of assumptions as to the ca- 
pacity and self-induction gave a correspond- 
ing series of curves. It would not be possi- 
ble to give a proper notice of Professor 
Eddy’s paper without reproducing many of 
his diagrams. 
Professor Alexander Macfarlane read an 
instructive paper on simple non-alternating 
currents. Professor A. G. Greenhill, of 
Woolwich, England, exhibited stereoscopic 
views of spherical catanaries and gyroscopic 
curves which were very interesting. The 
mathematics of each curve were given on the 
back of the card on which the stereoscopic 
projections of the curve were drawn. Pro- 
fessor Ernest Merritt read Dr. L. A. Bauer’s 
paper on the magnetic survey of Maryland. 
Professors G. 8. Moler and Frederick 
Bedell exhibited apparatus adapted to deter- 
mining the frequency of an alternating 
current. The instruments here included 
are twoin number. The first one, which 
has already been described by George S. 
Moler (Physical Review, March-April, 1897), 
consists of a small synchronous motor 
brought to speed by a crank handle con- 
nected with the motor by a suitable train of 
SCIENCE. 
651 
gears. The apparatus contains an electric 
ally operated speed counter, so arranged 
that its reading gives the exact value of the 
frequency of the alternating current with 
which the synchronous motor is suppliede 
The whole apparatus does not weigh over 
nine pounds. The reading is correct to 
within .05 of an alternation. The second 
instrument consists of a sonometer or 
monochord. The alternating current flows 
through a piano wire mounted upon a sound- 
ing board. The wire passes between the 
poles of a permanent magnet. By means of 
a sliding bridge the period of the wire may 
be made equal to that of the alternating 
current. This is indicated by the vibration 
of the wire. A scale is arranged so that 
the position of the bridge indicates the 
frequency directly. 
Dr. W. J. Humphreys gave an interest- 
ing account of some experiments on the ef- 
fect of pressure on the wave-lengths of the 
lines of the emission spectra of the ele- 
ments. He found a shift of the lines to- 
ward the red about proportional to the 
pressure and to the wave-length. The 
shift appeared to be independent of the 
temperature. Professor C. lL. Norton de- 
scribed a new form of coal calorimeter. An 
abstract of his paper is in the Electrical 
Engineer of September 9, 1897. The coal 
is burned with oxygen inside the calori- 
meter in a platinum crucible, on a very 
thin dish of platinum perforated with a 
large number of holes near the edge. The 
lightness and good conducting power of the 
platinum crucible and plate assure their 
being at a high temperature during com- 
bustion, and to this is due the completeness 
of combustion. No trace of carbon monox- 
ide and no indication of soot is to be found 
in the resulting gases. Professor E. B. 
Rosa read Dr. F. A. Laws’ paper on a new 
form of harmonic analyzer. An electro- 
dynamometer was used. A current sinu- 
soidal in character, and of frequency vari- 
