metallic tubes, placed in connection with the thick gilding that covered the whole exterior of the building; the points of the spikes there necessarily producing the effect of lightning-rods. How are we to suppose that it was only by chance they discharged so important a function; that the advantage received from it had not been calculated; that the spikes were erected in such great numbers only to prevent the birds from lodging upon and defiling the roof of the temple? Yet this is the sole utility which the historian Josephus attributes to them.” Upon a sober review of these facts, it is difficult to resist the conclusion that the ancient world had some proficiency in the art of guiding the electric fluid from the bosom of the clouds, conducting it in a prescribed course, and thus disarming it of its terrors. The subject of electrical agency is intimately connected with that of magnetism, to which this is the fittest place to glance—one of the most recondite points of physical science. The relation between the two is evident, from the notorious fact that lightning often renders steel magnetic, and disturbs the magnetism of the magnetised needle, so that in thunder-storms the compass needles of a ship have frequently been seriously injured. The magnetic agency, like electricity, has a general distribution over the earth, but the phenomena differ in different parts of the world, and are subject to periodical differences in the same place, the cause of which is very little understood. Every one is acquainted with the polarity of a freely suspended magnetic needle, or its tendency to lie parallel with the earth’s axis, pointing nearly north and south in every region of the globe. What is called the _dip_ or _inclination_ of the needle is its divergence from a perfectly horizontal position. Thus the north pole of the needle inclines downward in the latitude of London at an angle of 70°, but conveyed toward the equator, the dip diminishes, till no inclination at all appears. Transported farther toward the south, the dip again discovers itself, but in an opposite direction, the south pole of the needle inclining downward. “To understand the reason of this dip of the magnetic needle, and of its general direction, we have only to consider that the earth itself operates as a great magnet, the poles of which are situated beneath its surface. The directive property of the needle is owing to these poles; and when the needle is on the north side of the equator, the north pole of the earth having the greatest effect, the needle is attracted downward toward the north pole; hence exactly over the magnetic pole the needle would be vertical. Similar phenomena occur in the southern hemisphere; but here the south pole predominates, and of course depresses the corresponding pole of the needle; while at the magnetic equator, from the equal action of both poles, the needle will assume an exactly horizontal position.”