He informed us that the structure rested on a foundation consisting of a concrete mass, nine feet below the water line. Having ascended four flights of iron-wrought winding stairs, we reached the top of the circular structure; it having a diameter of twenty-four feet at its base, and rising to an elevation of fifty-seven feet. With great interest we inspected the revolving lights, exhibiting an ingenious piece of machinery, the invention of Finisterre and Barren in Paris, and representing a value of $1,800. This apparatus for rotating lamps is far superior to that for a fixed light. The characteristic of the latter is to constantly illuminate the whole horizon, requiring all the rays to fall simultaneously on the navigable track, whereas the demands made of a revolving light, are not nearly so great; only each point of the horizon being lighted at successive periods. When the dark intervals occur, the rays from the flame which are then pointing toward the obscure spaces, have their direction so altered laterally as to pass into the adjoining bright places; and so increase the power of the luminous flashes. A revolving light, though supplied by a flame of the same strength as a fixed, will thus necessarily be raised to a higher degree; for it does not lose its power by diffusing the rays constantly over the whole horizon, but gathers them up into a number of separate beams of greater intensity. The lights made to revolve by means of clockwork, were fed with mineral oil, a refined kerosine; and the refraction was caused by highly polished metallic reflectors. This visit to the Sand Beach Beacon was quite instructive; since we viewed there a practical application of an important principle in optics, based on the reflection of light. On Wednesday morning, the first beams of the new-born day had just appeared, when the yacht continued her voyage on Lake Huron. After a course of nearly twenty-two miles, we approached _Saginaw Bay_--the largest indentation on the western lake shore--comprising a width of thirty miles and a length of sixty miles. The passage across this bay, feared by many experienced navigators on account of the heavy ground swell, did not give us any cause for anxiety at first. Gradually, however, the sea became quite rough, and the enraged waves dashed their spray pearls even upon the deck of our sailing home. "The soft, wild waves, that rush and leap, Sing one song from the hoary deep: The south wind knows its own refrain, As it speeds the cloud o'er heaven's blue main."