158 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
resisting medium upon the velocity of a planet or comet,’ an effect 
often cited in the case of Encke’s comet. 
The theory of Lane takes no account of the rotation of the sun 
which is 25 times slower than that 
NP of the earth. M.Emden, taking his 
suggestion from Helmholtz, has filled 
Spot this gap and shown that, the given 
conditions remaining the same, the 
gaseous mass would separate into 
discontinuous layers slipping con- 
tinuously upon each other and. hay- 
ing the form of hyperboloids of one 
sheet.? (Fig. 4.) In the middle lati- 
tudes the slipping would be the 
greatest. This slipping produces 
through friction deep-seated eddies 
which could be the initial causes of 
sun spots and give a remarkable ex- 
planation of the zones in which they appear. Indeed, this seems to 
be the best explanation of the whole phenomenon. 
SIP 
Fie. 4. 
ELECTRIC AND MAGNETIC PHENOMENA. 
We haveso far treated only of the mechanical and optical phenomena 
of thesun. But we have every reason to suppose that the sun exhibits 
electric phenomena. All hot bodies do. Metals in particular (but 
not they alone) at high temperatures emit negatively charged particles 
(electrons) in great abundance. Richardson and Harker, at tem- 
peratures of about 1,500° obtained currents of 1 ampere per square 
centimeter of heated surface. The law connecting the current with 
the temperature is exponential. The emission from the sun must 
therefore be considerable. Further, the spectrum of the chromosphere 
includes a great number of lines which can be reproduced in the 
laboratory only by electrical processes. Finally, the sun spots have 
an undoubted although indirect influence upon terrestrial magnetism 
which is shown by the general concordance between the magnetic 
variations and the’ frequency of sun spots.2 We are thus almost 
inevitably led to conclude that the sun is magnetized, an hypothesis 
incompatible with its high temperature, or, and this is mfinitely more 
probable, that it is the seat of huge convection currents of charged 
matter. 
1It would seem at first sight as if a resistance ought to diminish the velocity. And so it would in an 
indeformable orbit as a consequence of the decrease of total energy. However, here the orbit is not invari- 
able and the interdependence of the elements alters the case in every way. 
2 The aspect of the corona especially toward the poles sometimes resembles these. 
2? We know that the latter vary periodically each eleven years. 
