22 
POPULAR SCIENCE REVIEW. 
meteor- streams annually intersected by tbe Earth, there are 
many varieties of orbit, from the hyperbola to the nearly circular 
orbit, calculated for the fireball of Nov. 27, 1877, by Major 
Tupman. The observed time of flight is the important element 
in the determination of meteoric orbits ; and it is unfortunate 
that accuracy is very seldom attained in this respect, and that 
sufficient attention is rarely given by observers to the estimation 
of a meteor’s visible duration. As to the number of meteor- 
showers at present ascertained, it is impossible to specify the 
exact figures. Several hundreds of well-defined systems are 
now included in our catalogues, and this department is enriched 
every year with new additions to its already extensive records. 
Previously unsuspected showers are constantly being brought 
to light by assiduous observations ; new meteor - epochs of 
decided intensity are becoming well established ; and many of 
the old showers receive frequent and ample confirmation during 
their annual recurrences. But though much has been achieved, 
more remains to be done in the future, for we are only just 
beginning to unravel the complicated details of the subject. 
Meteoric astronomy is but in its infancy. While other depart- 
ments of Science can number their centuries of research, this 
branch can only go back a few years to the time when Hei& 
first gathered the materials for its primitive elucidation, and 
the subject is so wide and difficult, requiring ages of diligent 
observation to explain the intricate and anomalous points it 
opens up for investigation, that it will be very long before we 
obtain a full knowledge of the principal meteor-swarms in their 
varied aspects, for they are as numerous as the stars in the 
sky ; and the extremely feeble nature of their apparition will 
for many years enable most of them to elude detection. The 
intermittent character of the true periodical showers will also 
allow them in some cases to escape the most vigilant eye, for 
becoming visible at very short intervals only once or twice in 
a long period of years they are very likely to be overlooked, 
though their special intensity will generally afford the means 
of their discovery. 
Meteors proceeding from the same stream present great 
similarity in their visible appearances, and if the observer is 
careful to note this in the case of each meteor seen, he will 
often be able to attribute the true radiant point though the 
path may be directed from the positions of several contemporary 
showers. Thus the Perseids of August 10 and the Leonids of 
November 13 are of great swiftness, frequently bright, and 
with the almost invariable accompaniment of streaks. The 
Or ion ids of October 20 are of the same character. The Geminids 
of December 10-12 are swift, short meteors without streaks. 
The Taurids of November are slow, sometimes trained, and 
