to an Astronomical Clock and Telegraph Register. 217 



They are also more uniform and less dependent upon the ner- 

 vous temperament of the individuals. They may be determined 

 in a few minutes' time by the astronomers, on meeting at the 

 same station, by striking alternate wires, each party being alter- 

 nately a leader. A few pairs of culminations printed in this way 

 fix the value of the equation if any exist. 



These views, which I have felt it my duty to lay before you 

 at length, are the result of a separate trial of each of the processes 

 involved in the art of imprinting dates. The experience of the 

 last summer furnishes some six hundred cases of imprinting dates 

 on an ungraduated fillet of paper. Dr. Locke's electro-magnetic 

 clock, on the 17th of November, furnished an ample trial of the 

 method of graduating the paper. 



The combination of the two operations so as to imprint the 

 dates of culminations on the automatic clock register, would have 

 been tried that night, but for the failure of the line from Pittsburg 

 to Philadelphia. The full trial, however, of the combination in 

 all its perfection, requires the construction of the proper instru- 

 ments ; with them, under your instructions, I hope, at an early 

 date, to submit these opinions to the test of practical experiment. 



Permit me to say a word on the experience of the Coast Sur- 

 rey in regard to the length of telegraph lines. This year we 

 made abundant experiments on the line from Philadelphia to 

 Louisville, a distance in the air of nine hundred miles, and in 

 circuit of eighteen hundred miles. The performance of this long 



line was better than that of any of the shorter lines has hitherto 

 been. 



t Not more than two or three good astronomical nights, at Cin- 

 cinnati and Philadelphia, were lost by failure of any part of the 

 Kne, in the periods of nearly two months of our stay at Cincin- 

 nati- I learn from an authentic source that the same success at- 

 tends the work from Philadelphia to St. Louis, a distance in 



CIRCUIT OF ONE-TWELFTH OF THE EARTH'S CIRCUMFERENCE. 



The number of Grove's pint cups used is about one for every 

 twenty miles. It is natural to conclude from this experiment, 

 that if a telegraph line round the earth were practicable, twelve 

 hundred Grove's pint cups, in equi-distant groups of fifties, would 

 office for the galvanic power for the whole line. 



The daily expense of acids for maintaining this motive power, 

 ^ou\d be about five mills per day for each cup, or six dollars per 

 da y for the whole line. 



Washington, December 1,'), 1848. 



Skcond Seribs, Vol. HI, No. 20— March, 1841). 28 



