404 
ME. LOUIS VESSOT KING ON THE SCATTERING AND 
Tabm II .—Constants of Atmospheric Scattering and Ahsorption. 
The coefficients of attenuation given in Table I. for various stations were plotted on a large scale diagram 
against as absciss;?. The results are shown in Diagram I. From the large-scale drawing the slopes of 
the straight lines passing through the mean position of the observed points were obtained and the values of 
tan 6' and tan 6” corresponding to short- and long-wave radiation were calculated.* From a knowledge 
of the mean barometric pressures at these stations the values of (i as defined in (75) Avere calculated for 
short-Avave radiation, leading by (84) to an estimate of No, the number of molecules per cubic centimetre 
of a gas at 0° C. and 7 60 mm. jAressure. The A'alues of the absorption constants F' and F" of (80) and (82), 
which include the effect of “ dust ” especially noticeable at low-level stations, are also giA'en in the table. 
At levels higher than Mount Wilson the atmosphere is comparatively dust-free and F' = F" = y. This 
Amine of y can then be employed in (78) to give a numerical estimate of molecular absorption. 
[* If greater accuracy is requii-ed the lines of closest fit to the system of observed points can be drawn by calculating in 
each case the position of the major axis of inertia of the corresponding system of material points of equal weight. Pormul* 
for the determination of this line are given by Kael Peaeson (‘ Phil. Mag.,’ vol. II., 6th series, November, 1901, p. .559), and 
also by Snow, E. C. (‘Phil. Mag.,’ March, 1911 ).—Note adrled iJecemher 31, 1912.] 
Table III .—Talmlation of tJie Fnnetion, Ce G{C (sec 1)}. 
The function G (.r) = (1 -e ■^)/x is tabulated by W. Lash Miller and T. R. Rosebrugh* in a set of 
extensive tables of the integrals 
[ u - e " du, 
f u ^ e ‘''du = Ei{- x), 
1 ue 
f e “ du. 
]x 
Jrr 
J^- 
Values are given to 9 significant figures at intervals of '001 betAveen x = 0 and x = 1, and at intervals 
of ’01 betAveen x = 1 and x = 2. From these tables the double-entry Table III. Avas easily constructed. 
The Ccilculations of the present table, as Avell as those of the other tables, Avere performed on a slide-rule, 
so that their limit of accuracy is about one or tAV'o parts in a thous;ind. 
* W. Lash Millee and T. R. Rosebrugh, ‘ Trans. Roy. Soc. of Caiiada,’ 2nd series, vol. IX., 1903, sect, iii., pp. 73-107. 
