338 SURVEY OF THE COAST 



In all cases, tlie application of Mr. Soldner's method oi 

 reducing all observations to the mean time, by correcting the 

 result for their respective distances from the same, applies 

 here with great ease and accuracy, since for each transit the 

 distances of tlie wires are equal on each side, as nearly as 

 the distances of the wires are, and tlierefore the calculation 

 of this correction maybe made for half their number only. 

 It will therefore always be found advantageous to apply this 

 method in the calculation of the results. 



This method of observing will be found very satisfactory 

 in practice, in regard to accuracy and a saving of time, toge- 

 ther with the facility of choosing it so as to come nearest the 

 prime vertical. 



This method will admit an observation of time to be taken 

 among flying clouds, when the method by repetition would 

 be inapplicable ; and when no complete observation can be 

 obtained, the observation of any pair of corresponding wires 

 in both positions of the circle will at least give an approxi- 

 mate result, which will often be useful. 



It would be very advantageous, in using this method, to 

 have five horizontal wires in the telescope within a space near 

 that occupied by the three, as the transits could easily be 

 observed, and the gain for each wire woidJ be double in tlie 

 result. I have therefore sometimes applied them. 



The registering of such an observation and the manner of 

 taking the result will be found in their proper places in the 

 Day-Book and the Journal of Results. 



Description of the Repeating Theodolite of One Foot Diameter. 



Besides the great theodolite, it was very desirable, as well 

 for the intended survey of tlie coast as for other uses in the 

 country, to have some instruments of the theodolite kmd of 



