Royal Society, 463 



distant one or more thousand miles. All the levels are to be read 

 with the instrument pointing to the zenith, then twenty bisections 

 of a circum-zenith star are to be imprinted on the automatic clock 

 register previous to reversal. The like number for the same star on 

 the same wires are to be imprinjted after reversal, and the levels are 

 again to be read. 



" A similar operation is performed for the transit of the same star 

 at the western station. 



"The primitive astronomical clock may be located and rated at 

 the central station of the coast survey. The automatic clock register 

 may be made and kept there, even if the distance be a thousand 

 miles from either station. 



" Clock registers in any number may be made at the separate 

 stations. The transits of two fundamental stars at remote dates, at 

 either of the three stations, may give the rate of the primitive or 

 central clock. 



" One such transit of the same star over each station with twenty 

 printed registers of normal bisections, and six normal levelings, with 

 independent levels, at or near the position of actual observation, 

 with the increased precision of the instrumental adjustments, will 

 give in the form of a permanent printed record (with multiplied 

 copies) the relative longitude of the two stations. 



" The uncertainty of such a result need be only a few hundredths 

 of a second, and may be such only as attends our present knowledge 

 of the relative longitudes of Greenwich and Paris, the two oldest 

 observatories extant. 



"I avail myself of the occasion to remark, that the Coast Survey- 

 operations were completely successful this autumn between Phila- 

 delphia and Cincinnati, while actually working on the line from 

 Philadelphia to Louisville. The distance of the line in the air is 

 nine hundred miles, that of the circuit is eighteen hundred. 1 learn 

 from an authentic source that the same success attends the use of 

 the line from Philadelphia to the Mississippi river opposite St. Louis. 

 The length of this circuit is one-tenth of the circumference of the 

 earth. The inference from this trial is clear, that a line round the 

 earth, if such could be constructed, might be worked with facility at 

 one stroke. The expense of acids to supply the thousand Grove's 

 pint cups, required for the motive power, would be about one pound 

 sterling (five dollars) per day." 



ROYAL SOCIETY. 



[Continued from p. 314.] 



March 29, 1849. — " Examination of the Proximate principles of 

 some of the Lichens." — Part II *. By John Stenhouse, Esq., F.R.S. 



Gyrophora pustulata. 



The author states that this lichen, which is the " Tripe de Roche" 

 of the Canadian hunters, has been long employed by the manufac- 



* [An abstract of Part L will be found at p. 300 of the 32nd volume of 

 this Journal. — Ed-] 



