ascertained to the hundredth of a second. On the wall of the recording room there was ranged a series of handles called switches, after the nomenclature of the railway. By moving these handles, you turned on the electricity to any particular instrument; so that every instrument in the establishment might he connected with the recording apparatus. The following figure shews the way in which the pen records
the time on the revolving barrel. It will be observed that the line traced by the pen is not continuous, but that it is broken by offsets, each of which marks a second of time. When an observation is taken, an additional and different offset is made by the pen, and it is only necessary to note the precise point in this broken line, where this offset is made, in order to determine the precise instant of observation. The intervals between the second's marks are sufficiently great, to enable an observation to be read off to the hundredth of a second.
In the dome was the great Frauenhofer telescope, alluded to as the best existing telescope. With the
