Professor Janssen, the well-known astronomer of Meudon Observatory, who has done more than any man living, perhaps, towards wedding the photographic camera with the telescope, has lately published some account of a marvellous picture which he obtained of ‘the old moon in the new moon’s arms.’ At the time that the picture was taken, the moon was only three days old, and an uncovering of the lens for one minute only was sufficient to secure the image. This image is feeble, but is full of detail, plainly showing the general configuration of the lunar surface. Professor Janssen believes that this application of photography points to a means of obtaining more precise measurements of the light, and of studying the phenomena which are produced by the double reflection of the solar light between our earth and its satellite. To the uninitiated, in these days of marvellous instantaneous pictures, an exposure of one minute may seem rather a long period. But let us consider for a moment what a very small proportion of the sun’s glory is reflected to us from the moon, even on the finest nights. Professor Sir W. Thomson gives some interesting information on this point. Comparing the full moon to a standard candle, he tells us that the light it affords is equal to that given by such a candle at a distance of seven feet and a half. As in the above-mentioned photograph the light dealt with came from a moon not full, but only three days old, it will be seen that Professor Janssen had a very small amount of illumination for his picture, and the only wonder is that he was able to obtain any result at all. It will be remembered that in the autumn of 1882, a series of observations were commenced in the polar regions, which had been organised by an International Polar Committee. Fourteen expeditions from various countries took up positions in that inhospitable area, with the intention of carrying out observations for twelve months, from which it was hoped that valuable knowledge would be gained. This programme has been successfully carried out, ten of the expeditions having returned home, many of them laden with rich stores of observations. Three remain to continue their work for another year. As to the return of the remaining band of observers—belonging to the United States—there is as yet no definite information.