TRANSACTIONS OF SECTION A. 901 
shown that this was due to imperfect contact through the insulating skin. By 
immersing the extremities in saline solutions, and using large leaden electrodes, 
this initial error was eliminated, and a fair approximation to the real value 
obtained. But additional difficulties at once presented themselves; firstly, in that 
the living body acts as a secondary battery, and sets up very appreciable counter- 
electromotive force ; secondly, that it has considerable electrostatic capacity, and 
acts to some extent as a condenser. 
The former of these might be minimised by alternating momentary contacts 
with a reversing key, but, even thus, later readings were always somewhat higher 
than the earlier, giving a resistance compounded indefinitely of real resistance and 
polarisation. The use of alternate currents from a small induction coil on 
Kohlrausch’s system, substituting a telephone for the galvanometer, an extremely 
elegant method, had occupied him for a year, but unfortunately it gives too 
low a result, probably from condenser action, and from the fact that a current 
rapidly reversed never actually traverses a very imperfect conductor like the 
human body, but only charges and discharges it in layers or sezments. 
Two opposite sources of error seem thus to be indicated, a condenser action 
spuriously lowering the reading, especially with alternate currents of high tension, 
and a polarisation action fallaciously raising it. The problem of ascertaining the 
amount of each of these was difficult. It had struck him, however, that the 
human body in many respects resembled a faulty submarine cable, in being at once 
2 conductor, a condenser, and an electrolyte. He therefore, on the advice of 
Mr. Latimer Clark, adopted a method employed by Sir Henry Mance, on the 
Persian Gulf cables, and described before the Society of Telegraph Engineers, on 
May 8,1884. It consisted in suddenly shifting the proportional coils of a specially 
constructed Wheatstone bridge (which was exhibited), and rapidly taking a 
fresh reading under the changed conditions. The values both of proportional coils 
and readings were then cross-equated so as to eliminate adventitious, and only 
retain intrinsic resistance. This method answered well, and gave results infinitely 
more concordant than any previously tried. For instance, two consecutive 
readings thus corrected gave 1,009 ohms and 1,007°8, a difference of less than one 
in 500, which was as near or nearer than could be expected in physiological 
electricity. He hoped thus to have overcome his first difficulty, and was 
endeavouring to meet those of measuring electrostatic capacity and opposite 
E. M. F. He already had roughly determined that the healthy body had a 
charging power as a secondary battery of about one volt or an ordinary Daniel 
cell, and he believed the chemical decomposition of tissue thus indicated was some- 
times, especially in cases of rheumatic sciatica, the cause of the cure which 
frequently, indeed almost invariably, ensued. 
9. On Contact Electricity in Common Air, Vacuwm, and different Gases, 
By J. T. Borromiry, M.A., F.R.S.E. 
The discussion at the British Association meeting at Montreal last year on the 
seat of electromotive force in the voltaic cell, the paper of Professor O. Lodge 
- which resulted from that discussion, and the subsequent discussion at the Society 
of Telegraph Engineers, must have brought forcibly before the minds of those 
interested in the subject the extremely unsatisfactory state of our experimental 
knowledge on some of the fundamental questions relating to contact electricity. 
Foremost among these, perhaps, is the question of the behaviour of various metals 
as to Volta contact effect in air and vacuum, and in gases different from common 
air. I have undertaken a series of experiments on this subject, and have already 
obtained some definite results; although the experiments which I have made up 
to this time are only to be considered as preliminary to a fuller inquiry. 
The apparatus which I am using is shown in the diagram. ‘The lower of the 
two plates to be experimented on is supported in the vacuum chamber by a small 
stand with a glass pillar, and the electrode from this plate passes through the side 
of the chamber, hermetically sealed into it. The upper plate is hung from the top 
