ASTRONOMY: A. VAN MAANEN 
133 
tions every year. Moreover, San Francisco where the number of health 
seekers is comparatively small, shows a contrast from season to season 
practically the same as at Los Angeles. I do not feel sure how to ex- 
plain this. It looks, however, as if the variable climate of the east 
causes people to become comparatively resistant to changes of tempera- 
ture, while the uniform climate of the Pacific coast although delightful 
in itself, causes people to lose the power of resistance and hence to suc- 
cumb quickly under adverse conditions. In table 5 localities are 
arranged according to the variability of their climates. The range 
between the highest and lowest death rates for the year is least in New 
York where the climate is most variable, and greatest in Los Angeles 
where the climate is most uniform. 
THE PARALLAX OF THE PLANETARY NEBULA N. G. C. 7662 
By Adriaan van Maanen 
MOUNT WILSON SOLAR OBSERVATORY. CARNEGIE INSTITUTION OF WASHINGTON 
Communicated by G. E. Hale, December 24, 1916 
The first results for the determination of stellar parallaxes obtained 
with the 80-foot focus arrangement of the 60-inch reflector were com- 
municated to these Proceedings about two years ago.^ The promis- 
ing outcome of that investigation was fully confirmed by later results; 
the small probable error and the apparent absence of large systematic 
errors showed the desirability of extending the work to some of the 
nebulae. The parallaxes available for these interesting bodies are as 
yet extremely rare and the few existing results are far from trustworthy. 
For instance, about half a dozen determinations for the large spiral 
nebula in Andromeda have been published, the results ranging from 
-0^32±0M2 to -fOM71±OV05P. 
Six nebulae were accordingly added to the Mount Wilson parallax 
program. In most cases the necessary exposure times are considerable 
and for several fields the work cannot be finished for some time. The 
planetary nebula N.G.C. 7662 ( = H IV 18 Andromedae), which has a 
sharp stellar nucleus, gives good measurable images in a 25 minutes 
exposure (see Plate). Sixteen exposures were secured, the details 
of which are given in table L The successive columns contain the 
plate number, the date, the hour angle in degrees, the initials of the 
observer (H = Hoge, vM = van Maanen), the quality of the plates, 
the parallax-factor, the factor for annual proper motion, and finally 
some remarks. 
