PROGRESS OF METEORIC ASTRONOMY IN AMERICA. 297 
so as to enter the solar system having little or no cohesion, 
like a mass of pebbles; or it may have come, and probably 
did come, a single solid stone. 
In either case, as it got near to the sun new and strong 
forces acted on it. 
The same heat and repulsion that develops and drives off 
from a comet in one direction a tail, sometimes a hundred 
millions of miles long, may have cracked off and scattered 
in another direction solid fragments. One of these contained 
in it this stone, and it wandered in its own orbit about the 
sun, itself an infinitesimal comet, how many thousands of 
millions of years we know not, until three years ago it came 
crashing through the air to the earth in Iowa.” 
More than ordinary space has been given to the citations 
from the various statements and arguments and to the con¬ 
cluding speculation of Professor Newton’s paper because, 
better than any preceding American discussion, it presents 
the status of the modern theories of meteors and comets 
which are now generally accepted by the scientific world. 
The latest formal discussion of this subject was presented 
by Professor Newton 1 in his presidential address before the 
American Association for the Advancement of Science, at 
Buffalo, in 1886. This address was devoted wholly to the 
consideration of the various-theories in regard to the motions, 
character, and origin of meteorites, meteors, and shooting- 
stars. 
The discussion in this address follows the same general 
lines as in the lecture just cited, while the various arguments 
are presented with far greater elaboration. No new hypoth¬ 
eses or theories are offered ; but the key-note of the address, 
given in the author’s own words, is that “ science may be 
advanced by rejecting bad hypotheses as well as by forming 
good ones.” 
1 Proc. Am. Ass. Ad. Science 1886, 1. 
