The _Bielids_, or _Andromedids_, are connected with Biela’s comet, and have a period of 6¾ years. We are now aware of meteor streams which at certain stated intervals, cross the earth’s orbit. They are regular visitors for which we may watch with every certainty that a few, if not thousands, will be captured by too near an approach to the atmospheric net encircling our planet. The whole of the solar domain may be alive with meteors, but by no possibility can we become aware of their presence until they take the fatal plunge which ultimately causes their destruction. The space actually traversed by the earth in its journey around the sun, is but the minutest fraction of that vast sphere over which the sun holds sway, “yet it has been estimated by Professor Newcomb of America, on grounds which are perfectly reliable, that in including telescopic meteors (that is, meteors so small as only to be visible when they happen to pass across the field of view of a telescope), no less than 146,000 millions of meteoric bodies fall each year upon the earth. If one in a thousand struck a human being the inhabitants of the earth would be decimated in a single year.” (R. A. Proctor, _The Expanse of Heaven_, p. 164.) Fortunately for us, the earth is protected by the surrounding air, which offers a most effective resistance to the swift motion of the celestial missiles with which it is bombarded from above. The swifter their motion, the more effective the resistance. When meteors are first seen they are mostly at a height of seventy miles, vanishing at a height of about fifty miles. But the actual course they pursue through the air is nearly always much longer, because they do not descend vertically, but aslant.