p6 A CONTINUOUS RECORD OF ATMOSPHERIC NUCLEATION. 



in this way would gradually decrease toward the end of the experiment so that 

 the slopes of all curves compatibly with the observations would gradually be 

 the same. Below the middle g-b-p coi'ona, the cvirves if placed together would 

 nearly coincide. The difficulty with this hypothesis is the absence of any 

 obvious effect when the time between observations is varied. The curves are 

 about the same for 6t = 2 min., 3 min., or even 12 min., so far as observed. 



36. Subsidence. — The effect of errors in the subsidence constant may be 

 estimated. Writing the equation n^ = n„io^-~^^'"'^^'n, in the approximate form 

 «. = n„io*=-^'>-Mi--S(i| +^^. + i| + , + )), whence if iV=io<-^"-^ 



It is preferable to use the inverse method, putting n„ = n^/N {i — S2{^)), 

 whence (5;?o = '^:2(A) SS. 



Putting «2= 10500, »o= 212000, .¥ = .0703, 2{j^) = .26s, 



6n^ = 40000 6S, nearly. 



Thus if (lS = .2, 6n^ = Sooo, or relatively 8000/212000 = . 038. It follows 

 that by the error of .2 made in the estimate of 5, n^ will not be affected more 

 than about 4 per cent., which in no way accounts for the observed discrepancy 

 of the new and the old results. 



37. Exhaustion ratio. — Again if the above vakie of n^ be taken, the effect 

 of an error in the exhaustion ratio y will be 



-6nJn,= '^'iz-Z)6y. 



For n„ = 212000, z — Z=ie,-S' y = -7(>7, an average case in the preceding 

 table, 6n^/n^= iT,6y, or for 



6y=.i -6njn„= 130% 



.05 6s % 



.01 13 % 



showing that great care is needed in relation to y. 



38. Inferences. — To reach an opinion as to the cause of the observed 

 initial diversity of rates one may note that for equal |)ressvire differences, smaller 

 nuclei are necessarily caught by the instantaneous valve than by the stoxjcock. 

 More nuclei are thus within reach in the former case: but apart from this, 

 since all other conditions are the same for both cases, the rate of denucleation 

 should be the same, even if the absolute number of efficient nuclei removed by 

 exhaustion is greater for the instantaneous valve. If therefore one begins with 

 the same corona which implies identity of diameter of particle and may be as- 

 sumed to imply an identical number of available or effective nuclei in both cases, 

 the two ctirv^es shovild be identical. In figures 12 and 13, considered first be- 

 tween the upper w-y-o and the middle g-b-p corona, the new and the old curves 

 cross at the large w-y-o corona. If under identical exhaustions the number of 

 available nuclei are therefore successively greater for the instantaneous valve 



