‘710 -., REPORT——1896, 
diffused by all substances than rays of greater deflectibility. 1t might therefore 
be expected that there exists an extreme form of cathode rays which is not per- 
ceptibly. deflected by a magnet, and which is accordingly very slightly absorbed 
and diffused by all substances, but which would have the same property of being 
absorbed by all substances approximately in proportion. to their density. The rays 
discovered by Réntgen agree in these respects with such cathode rays; they agree 
with them also in other respects, and, in fact, no observation yet made contradicts 
the hypothesis that the Rontgen rays are of the same nature as the cathode rays, 
being an extreme form of cathode ray with zero deflectibility. \ 
2. On the Laws of Conduction of Electricity through Gases exposed to 
the Réntgen Rays. By Professor J. J. Tuomson, F.RS., and 
E. RUTHERFORD. 
[Published in the Phil. Mag., Nov. 1896, pp. 392-417.] 
3. On the Transparency of Glass and Porcelain to the Réntgen Rays. 
By A. W. Ricker, F.R.S., and W. Watson, B.Sc. 
‘The transparency to the X-rays of a number of different pieces of the same 
kind of glass up to a total thickness of 5'1 mm. was determined by the photometric 
method. 
The results can be expressed very approximately by the formula 
I =I, {0-2 + 0°8 x 0:35794,3, 
where I, is the intensity of the phosphorescent light when no absorbing medium is 
interposed, and I the intensity when the X-rays have passed through ¢ mm, of the 
glass used. This suggests that the rays emitted. by the tube consist of two great 
groups, to one of which the glass is very transparent, while the remainder are 
absorbed according to the ordinary law. - * 
Observations were then made on the ratio between the transparency of different 
kinds of porcelain to that of glass of the same thickness. The specimens were in 
part lent by the authorities of the South Kensington Museum, and were in part 
selected from a small collection belonging to one of the authors. 
The mean results were as follows :— 
Bow opaque. 
Phosphatic Soft Paste  . : ri ery BE aeons ; : 4 
Crown Derby .:: °a... =~ O27 
Soft Paste ‘ ; - r . . Worcester . - ates . 036 
_ Hard Paste ‘ 3 z : .__ Bristol Cottage Ware : . 0:56 
Soft, but glass-like Paste. ; | poe Loam Beaphts . Aes 
; Ny Po Gecio . Soee 
Hard Paste - » . = Bionenpar eet “ut i 0-93 
4, Measurement of Electric Currents through. Air at different Densities down 
to one Five-millionth of the Density of Ordinary Air. By Lord 
- Ketvin, J. T. Borromney, and Macnus Maciean. 
The apparatus used in these experiments consisted of (1) a cylindrical tube 
13 ems. long and 13 cm. diameter, with two aluminium wires as terminals ground 
to points 15 cm. apart; (2) a large Wimshurst electrostatic machine of 
24 plates; (8) a high-resistance mirror galvanometer to measure the current 
between the aluminium-point terminals inside the tube; (4) an electrostatic volt- 
