1880.] Scientific Progress of the Past Year . 13 
resulting from Radiation,” and has already struck out into 
a new region, viz., the study of certain Electrical Phenomena 
which appertain especially to high vacua. In the vacua to 
which he has now turned his attention the exhaustion has 
been carried even beyond that in which the phenomena of 
the Radiometer are produced, and it is by a legitimate and 
sagacious step that he has now occupied a complete field of 
inquiry intermediate to the most extreme vacua ever attained, 
and those in which the stratified discharge is displayed. Of 
the delicacy and beauty of the experiments it is not neces- 
sary here to speak, for they have been already exhibited 
here, as well as to more than one audience on a large scale. 
Through this advance on his part a helping hand will 
doubtless be held out to those who are occupied with the 
subject of stratification, for in this matter the two advancing 
powers desire neither a “ neutral zone ” nor a “ scientific 
frontier ” to separate their field of action. 
Another communication, full of promise as well of per- 
formance, should also not pass unnoticed. I allude to Prof. 
Hughes’s paper on his Induction Currents Balance, the 
application of which has already branched out and borne 
fruit in more than one direction. The extreme simplicity of 
the instruments, and their marvellous adaptation to the 
purposes for which they were intended, refleCt the highest 
credit on their inventor. 
Not unconnected with Mr. Crookes’s researches, so far as 
they are directed towards the ultimate constitution of gases, 
are those of Prof. Osborne Reynolds. In his remarkable 
paper “ On Certain Dimensional Properties of Matter in a 
Gaseous State ” Prof. Osborne Reynolds has established the 
faCt of what he calls Thermal Transpiration, namely, that 
when two portions of the same gas are separated by a 
porous plug, the two surfaces of which are at different tem- 
peratures, the condition of equilibrium is no longer that the 
pressures of the gas on the two sides of the plug should be 
equal, but that the pressure on the hotter side should exceed 
that on the colder side by a certain quantity ; and that if 
this is not the case, the gas will transpire through the plug 
until this condition is satisfied. Prof. Reynolds conneds 
this principle with Mr. Crookes’s Radiometer experiments ; 
and the various considerations which he brings to bear on 
the subjeCl appear to have this idea throughout, that the 
dynamical similarity of two gaseous systems, bounded by 
solid surfaces, geometrically similar, depends on the ratio of 
the homologous lines of the system to a certain quantity, 
having the dimensions of a line, and which varies inversely 
