1866. ] Astronomy. 569 
mass must have been small, since the fall of a mass as large as the 
earth upon the sun would, “from the conversion of its previous 
mechanical energy, give out such a blaze as would in a moment 
scorch up all the inferior planets and probably the earth also.”* 
He finds that even if the blaze were persistent, the general rise of 
temperature would not ‘exceed 15°; but since the extra power of 
radiation would only act during the short time occupied by the 
body in passing through the solar atmosphere before plunging 
under its surface, the blaze would not be persistent. The general 
temperature of that part of the sun would be very sensibly in- 
creased, but the whole potential radiating power of the sun would 
not be increased in a perceptible degree. And even assuming that 
this power were increased 1,000°, yet, since the potential tempera- 
ture which sends heat enough to maintain the earth’s temperature 
(at an average) 500° above absolute zero is about 12,000,000°, the 
effect would only be to raise the earth’s mean temperature ,!.th of a 
degree. Therefore, no perceptible change of climate can be expected 
to accrue from an accession to the sun’s mass approaching the earth 
in magnitude. “The only indication,” he says, “which we can 
become cognizant of is the possible decrement in the length of the 
ear.” 
: Mr. Waterston proceeds to obtain and apply an approximate 
formula for determining the amount of this decrement. It results 
from this formula that a sudden increase of the sun’s mass by a 
mass equal to our earth, occurring at the time of observation (Sep- 
tember), would have resulted in a decrease of the major axis of the 
earth’s orbit by 261 miles; and the length of the year would 
accordingly be diminished by 130 s., corresponding to an accelera- 
tion of the sun’s mean (apparent) motion by 5”°3 ina year. Had 
the increase of the sun’s mass occurred in July, the major axis 
would have been diminished by 255 miles, while the decrement 
would have been no less than 281 miles had the increase of mass 
occurred in December. In all cases the line of apsides would 
progress. 
It may be remarked that the question of the effect of an 
increment in the mass of an attracting body has a bearing on 
a subject that has lately attracted much attention—the acceleration 
of the moon’s mean motion. For it has been calculated by 
Reichenbach, that, on an average, at least twelve meteoric bodies 
fall daily upon the earth’s surface, so that in 1,000 years upwards 
of four millions of these bodies must have been added to the earth’s 
mass. Such an increment is almost infinitesimally small, no doubt, 
compared with the earth’s mass, but, so far as it goes, it is an 
effective cause (i) of acceleration of the moon’s mean motion, and 
(1i) of retardation of the earth’s rotation. 
* “Monthly Notices,’ vol. xx., p. 89. 
