when the dynamos
were connected direct. In the former case the increase of volts was
proportional to the length of main used, and 8,500 at Deptford gave
10,000 at London.

Mr. Blakesley described a simple method of determining the loss of
power in a condenser by the use of three electrodynamometers, one of
which has its coils separate. Of these coils, one is put in the
condenser circuit, and the other in series with a non-inductive
resistance r, shutting the condenser. If a_{2} be the reading of a
dynamometer in the shunt circuit, and a_{3} that of the divided
dynamometer, the power lost is given by r (Ca_{3} - Ba_{2}) where B and
C are the constants of the instruments on which a_{2} and a_{3} are
the respective readings. Prof. S.P. Thompson asked if Mr. Swinburne
had found any dielectric which had no absorption. So far as he was
aware, pure quartz crystal was the only substance. Prof. Forbes said
Dr. Hopkinson had found a glass which showed none. Sir William
Thomson, referring to the same subject, said that many years ago he
made some tests on glass bottles, which showed no appreciable
absorption. Sulphuric acid was used for the coatings, and he found
them to be completely discharged by an instantaneous contact of two
balls. The duration of contact would, according to some remarkable
mathematical work done by Hertz in 1882, be about 0.0004 second, and
even this short time sufficed to discharge them completely.

On the other hand, Leyden jars with tinfoil coatings showed
considerable absorption, and this he thought due to want of close
contact between the foil and the glass. To test this he suggested that
mercury coatings be tried. Mr. Kapp considered the loss of power in
condensers due to two causes: first, that due to the charge soaking
in; and second, to imperfect elasticity of the dielectric. Speaking of
the extraordinary rise of pressure on the Deptford mains, he said he
had observed similar effects with other cables. In his experiments the
sparking distance of a 14,000 volt transformer was increased from 3/16
of an inch to 1 inch by connecting the cables to its terminals. No
difference was detected between the sparking distances at the two ends
of the cable, nor was any rise of pressure observed when the cables
were joined direct on the dynamo.

In his opinion the rise was due to some kind of resonance, and would
be a maximum for some particular frequency. Mr. Mordey mentioned a
peculiar phenomenon observed i