The authors attempt to derive some fundamental properties of the atmospheres of comets from collected photometrical quantities, primarily of classical photometric parameters.
In the first part various, currently used methods of measurements are being evalulated and some modifications or applications of them suggested. The authors point at the main insufficiencies of the methods, consisting, first of all, in the fact that the majority of them canot be cosidered as measurements in the proper meaning of that word.
In the second part the physical significance of the photometrical parameters is being theoretically interpreted. On the basis of actual material it was found that the gas-dust model of the atmospheres of comets is an acceptable explanation of the dependence of photometrical parameters on the heliocentric distance.
In the last part it has been briely demonstrated that in some cases, particularly in those of short-period comets, the alteration of the photometrical parameters with time need not be caused by change in the percentage of the meteoric dust, dispersed in the coma. The total amount of dust at the moment of observation is in comets with a continuous spectrum of the order of 10^11 g.
This paper presents measurements of the polarization of light in the tails of the comets Arend-Roland and Mrkos, made in the total photographic light. Results given in Tables II and V indicate that the tail of the Arend-Roland comet contained a substantial dust component, while the polarization in the tail of the Mrkos comet can be explained predominantly by pure molecular emission.