84 Barus — Geometric Sequences of the Coronas of Cloudy 



In two successive experiments which showed a reasonable 

 order of agreement, the color sequences of the coronas were 

 observed from the center outward, while the corresponding 

 flame or axial colors were simultaneously noted ; but here there 

 is an uncertainty from the small relative thickness (30*5 cm.) 

 of the axial layer of water particles. Table I contains the 

 results. Where different colors were seen (which may either 

 be errors of judgment, or real differences of closely contiguous 

 coronas) they are noted by inserting both colors on a line. 

 The colors being fleeting, it is out of the question to wait for 

 rigorous isothermal conditions; neither is it certain that the 

 colors were caught for the adiabatic state of compression. A 

 small allowance of time after exhaustion must be granted for 

 judgment. The general agreement of coronas obtained seemed 

 to vouch for this method of combating, partially at least, an 

 inherent difficulty. The computation will be made both for 

 isothermal and for adiabatic conditions, leaving the true result 

 to be derived below, § 5. 



Ignoring decay and similarly spontaneous time losses due to 

 the motion of the nucleus, I here obtain a scale of optical 

 effects related to the nuclei in a given volume of air saturated 

 with aqueous vapor and to the given exhaustions. As more 

 particles are present the condensed water globules are finer, 

 remembering that the medium is always identically super- 

 saturated. Only the momentarily fixed corona following the 

 exhaustion has a real meaning. 



The axial color or color of the full flame is seen to make up 

 a similar sequence ahead in phase and nearly complimentary 

 in color to the central patch of the corona. This will be 

 separately investigated below, § 7. 



The advantage of a geometric distribution of coronas will 

 appear in the attempt now to be made to remove the time loss, 

 which is also probably geometric. 



4. Loss of nuclei in the lapse of time. — To determine in how 

 far such an interpretation as given in the last paragraph is 

 admissible and to correct it for the other simultaneous losses, 

 it is necessary to determine the decrease of nuclei when the 

 receiver is left for long intervals as far as possible without 

 exhaustion or manual interference. In the following experi- 

 ments the time between the inevitable exhaustions (usually 

 about 96 sec, above) is prolonged to thirty minutes or even an 

 hour. The first column in Table II shows the number of the 

 exhaustion (with refilling of filtered air), the second the time 

 elapsed since nucleation, the third the color sequences of the 

 corona obtained. These are as a rule easily recognized by 

 comparison with Table I, and the coronal number or " order" 

 is put in the next column. It may be noted that fogs are often 



