Experimental Researches on Gravitation. 495 



down on the abscissa, and the ty values on the ordinates ; 

 in this way the curve corresponding to equation (15) is 

 obtained It touches the axis of the ordinates with a value 

 1 (see (8)) ; and it is asymptotic to the axis of the p's. 



Application of the ty function to the Sun. — The sun's density 

 is assuredly not uniform ; but for a roughly approximate 

 research I shall suppose this density to be constant, and 

 equal to 8 . Its apparent density is the astronomical one, 

 and we have S a = l'41. Several hypotheses can be made as 

 to the real value of 8 V for the sun ; for each of them one can 

 calculate the value of ^ by means of (7) ; then, from the 

 curve of fig. 2, the corresponding value of p can be deduced ; 

 and finally, since jo = B-H = R J? S l7 /i, we can deduce the value 

 of h, seeing that the sun's radius is B* = 6*95 . 10 10 cm. We 

 can construct the following table : — 



^=1-41 2 5 10 15 20 



$=8J8 v ==l 0705 0-281 0*141 0'094 0"070 



p=0 0-53 2-46 5-20 795 10-40 



p/nj v =0 3-81. 10" 12 7-08. 10~ 12 7-49. 10~ 12 7-63.10~ 12 7-64.10 -12 



Hence we see that if the true density is increasing, the h 

 value increases rapidly, up to a density of about 2 ; and 

 then more slowly, with a tendency towards a limit-value 

 that we can see remains fixed at 7*G5 . 10~ 12 . 



Furthermore, we can see that, even admitting only a true 

 density of the sun slightly greater than the apparent (i. e. 2), 

 the order of magnitude for the h quenching factor remains 

 fixed between 10~ 12 and 10 -11 . 



The h factor. — According to the already made hypothesis, 

 the h factor represents a universal constant, upon which the 

 measure of the gravitational absorption depends ; and its 

 probable value would be, as aforesaid, fixed between 10 ~ 12 

 and 10 -11 ; but its exact determination cannot be arrived at 

 by considering the solar phenomenon. In fact, we lack the 

 necessary elements to enable us to state the true density of 

 the sun ; perhaps we can believe it to be certainly greater 

 than 1'41 (apparent or astronomical density), when we 

 consider the great density of some heavier bodies. The 

 sun's very high temperature, that would have the effect of 

 dilating to an enormous extent such bodies, might be com- 

 pensated by the enormous pressure in the solar mass interior. 

 Anyway the value of the aforesaid true density of the sun 

 cannot be established a priori with sufficient exactitude. 



We can then imagine an experimental method for the 

 investigation of the h constant. It would consist in finding 



