1 i^ Royal Astronomical Society. 



ROYAL ASTRONOMICAL SOCIETY. 

 [Continued from vol. xxxv. p. 525.] 



Dec. 14, 1849. — The Astronomer Royal gave an oral statement, 

 illustrated by models and diagrams, " On the Method of observing 

 and recording Transits, lately introduced in America ; and on some 

 other connected subjects." 



The Americans of the United States, although late in the field of 

 astronomical enterprise, have now taken up that science with their 

 characteristic energy, and have already shown their ability to instruct 

 their former masters. The method of observing which it is the ob- 

 ject of this lecture to explain, was apparently suggested at first by 

 the obvious practicability of applying the Galvanic Telegraph (so 

 extensively used in America) to the determination of differences of 

 terrestrial longitude ; and it was first used for the differences of 

 longitudes of the cities Louisville, Cincinnati, and Pittsburg. It ap- 

 pears that this first application of the principle is entirely due to Dr. 

 Locke of Cincinnati. It became, however, evident that the same 

 method might be used conveniently for recording the observations 

 made at one or at several instruments in the same observatory ; and 

 Professor Mitchell, also of Cincinnati, actually prepared an apparatus 

 at the Observatory at Cincinnati, and with it made observations, 

 specimens of which have been sent to individuals in this country. 

 One of these specimens was exhibited by the Astronomer Royal to 

 the meeting. Between the systems of Dr. Locke and Professor 

 Mitchell there is one radical difference, namely, in the principles of 

 giving the signal of observation ; in the principles of recording the 

 signal there is also a difference, but this difference is not essential, 

 and there appears to be no reason why the same method of making 

 the record should not be used in both systems. It will perhaps be 

 most convenient to begin by describing the methods of making the 

 record, which are, or may be, common to both systems. 



The general principle of the methods, as regards the act of the 

 observer, and its difference from the act in the ordinary observation 

 of transits, is the following : — In ordinary observations the observer 

 listens to the beat of a clock while he views the heavenly bodies 

 passing across the wires ; and he combines the two senses of hear- 

 ing and sight (usually by noticing the place of the body at each 

 beat of the clock) in such a manner as to be enabled to compute 

 mentally the fraction of the second when the object passes each 

 wire, and he then writes down the time in an observing-book. In 

 these new methods the observer has no clock near him, or at least 

 none to which he listens ; he observes with his eye the appulse of 

 the object to the wire, and at that instant he touches an index, or 

 key, with his finger ; and this touch makes, by means of a galvanic 

 current, an impression upon some recording apparatus (perhaps at a 

 great distance), by which the fact and the time of the observation 

 are registered. He writes nothing, except perhaps the name of the 

 object observed. 



The method adopted by Dr. Locke was that of interrupted indented 

 lines, produced by the pressure of a point or style (effected by a gal- 



