676 Prof. M. Smoluchowski-Smolan on the 
forming thermoelectric couples, by rapid motion in air, have 
established its approximate proportionality to the square of 
velocity and its independence of the substance and dimensions 
of the moving body (about 1° C. for 55 — in the limits of 
30-100 = ; thus, denoting the coefficient of proportionality 
by f(@, p), we shall have 
AO=W KO, py): 
By supposing («= B=h=n= een ®) there results a 
similar movement, with unchanged A@, u, but changed 
pressure ; whence we have 
S(9, p) =f, po). 
Thus the heating effect A@ must be independent of pressure; 
and similarly there follows by 
(2=B=b=1; m=/h; n=h*3) 
its independence of the temperature. 
Moreover, comparison of different gases 
@=m=h>=b=1; n=), (b=m=—b=1;5 fae ee 
demonstrates its independence of their viscosity, but pro- 
portionality to their molecular weight. 
These results may be embraced by the formula 
, Ad=aMvw’, 
where a is the same constant for all gases (provided & be 
equal). 
If its extrapolation beyond the velocity of sound were 
allowed—which seems improbable-—we should infer from it 
a heating effect of 2500° C. for a meteor moving with a speed 

of a No conclusions can be drawn as yet about the 
effect. of small velocities (in Kelvin’s experiment below 
30 a where the above empirical formula is not applicable 
and where the measurements were not sufficient to define the 
modification required. 
§ 10. Let us consider, now, in a similar way the flow of 
gases through pipes and holes. To the extreme case of a 
small difference of pressure on both sides of a capillary tube, 
there applies the law of Poiseuille-Graham-Meyer, 
rh rr Po—P1 
, Ta Su ~ 
