ABSTRACT:- In the calculation for v, the velocity for small undercooling, from Hillig and Turnbull (1956) 0.01 < ΔT < 10 Kelvin, where ΔT is the degrees of undercooling and they say that v = (D ΔS ΔT) / (l R T), that is, according to simple rate theory by Wilson (1900) and Frenkel (1932). To estimate ΔT, I reason you have to take the geometric mean, GM, of 0.01 and 10. That is GM = ( 0.01 x 10 )1/2 = (0.1)1/2 = 0.316. In my snow point paper, Jennings (2023), I had said ΔT < 0.5 Kelvin, so that was correct in the first place. In Hillig (1958), p. 351, there is the comment that larger undercoolings are 0.5 Kelvin. In Jennings (2023) the author gets T = D (7.15 x 107 ) / (k a ns ΔT 0.69) for T, the snow point for formation of ice from water. The expression for T, the snow point, comes from homogeneous nucleation theory as employed by Fletcher (1970). ΔT = To – T, is the underooling for formation of ice in the cloud.
To is the melting temperature Kelvin of ice. The reason there is an undercooling is because it is applied as measured in a thermostat bath. It is an assumption that this applies to clouds, as said by Jennings (2023). The process of using the bath will be explained in this paper.

KEY WORDS:– undercooling “snow point” “homogeneous nucleation theory” “geometric mean”