The telescope of six inches aperture, easily handled, is inclosed in a sort of cabin which rolls on wheels. This can be pushed backward a certain distance, leaving the instrument out in the open air. Fortunately, the width of the cabin was such that it was just possible for the writer to catch hold of the rods on each side, drawing them backward the distance required; while shutting it was an easier matter, requiring as a rule a gentle push, sending the cabin back on the rollers provided for this purpose. Before doing so, however, the telescope was leveled and carefully wrapped up to keep it free from any moisture or dampness which might penetrate from the outside, and anyone who has passed a winter in Wisconsin knows something of the deep snowdrifts which must settle several feet deep in such an exposed site as the main roof of the Yerkes Observatory building. After the cabin has been closed, it is hooked at the sides and remains so until the services of the telescope within are once more required. [Illustration: THE COMET-SEEKER ON THE ROOF OF THE YERKES OBSERVATORY, AT WILLIAMS BAY, WISCONSIN ] Then the cabin is reopened and the wrappings are removed from the telescope, which is turned in the direction of a specially selected star. This is kept in the center of the field of view, which is marked by the intersection of two threads made from a spider’s web. As there is no clockwork attachment, the telescope is guided by means of a small screw like a miniature wheel or helm, enabling the observer to pilot his or her way through the ocean of space. Then a keen search is made in the surrounding region, and if nothing in the way of a comet “stands revealed” to the searching eye of the telescope, another region is explored, so that a more or less extended expanse of sky comes under observation during the course of the evening. On one eventful occasion a supposed comet was glimpsed and its position duly charted with regard to neighboring stars. However, on reference to the star map the fuzzy-looking object proved to be a nebula. Supposing by any possibility the suspected object _had_ been a comet, this could have been proved beyond doubt by watching it for two or three evenings in succession. The presence of a comet can be detected as it slowly drifts against a background composed of the stars, while the nebula is at a distance so remote that an observer would have to watch for centuries before he detected any perceptible motion.