At the Philadelphia meeting an account was given of experiments to detect ether drift. These observations gave no indications of a drift of the ether. It has been suggested that the negative results are due to the influence of the heavy stone walls of the building within which the apparatus was mounted. The interferometer has, therefore, been mounted on high ground near Cleveland, and covered in such a manner that there is nothing but glass in the direction of the expected drift. It was much more difficult to make observations in this location than in the building; satisfactory observations could only be made on a cloudy evening following a cloudy day, when the temperature changed very slowly. The temperature effects could never be entirely eliminated. The conclusion from many observations is that there was no indication of a drift of the ether through the interferometer. The expected drift would produce a displacement of the interference fringes of 1.53 wave-lengths; the above result is probably certain to one eightieth part of the whole.
