HARVARD COLLEGE OBSERVATORY.

The following announcement is made in conformity with instructions received from Professor E. C. Pickering, the Director of the Observatory.

On and after Sunday, November 18, 1883, the telegraphic time-signals sent automatically from this Observatory will conform to the time of the seventy-fifth meridian, to be known as "Eastern Time." This time is exactly five hours slower than Greenwich Mean Time. and 15 minutes 44.5 seconds slower than Boston State House Time heretofore furnished. It is intended that the new time shall be given to the public at noon on the Sunday named above; but as the Observatory signals are the means by which the persons in charge of -public time-pieces will make the necessary preparation for the change, it has been decided to furnish the new signals at an earlier hour. Attention is therefore called to the following arrangement.

The signals given according to State House Time will stop at Greenwich midnight, Saturday, November 17, 1883; that is, at about 7h. 16 P. M., by the local time. The signals according to "Eastern time" will begin at Greenwich noon on Sunday, November 18; that is, at 7h Om A. M., by the new standard. The minute immediately preceding 7h A. M. will be entirely occupied by a long rattle of about 36 seconds and a pause of about 24 seconds. This will also occur during the minutes immediately preceding the hours 8, 9, 10, and 11, A. M. The first of the regular two-second beats following the pause will indicate the precise hour.

J. RAYNER EDMANDS,Assistant in Charge of Time Service. Harvard College Observatory,