90 On the T rigonometrical Survey 



been calculated, and the latitudes at several main stations? 

 both from the local observations and by the tri angulation 

 commencing at Hobart Town, have been computed with the 

 true bearings of lines meeting at the same stations. 



With a view to show more particularly the nature of the 

 field operations, and of the computations and the results, I 

 append to this Eeport extracts from the Field Books and 

 examples of the method of calculation adopted. I have 

 given also a comparison of the results of the calculations for 

 latitude and true bearings, as derived from the local observa- 

 tions at each station, and as derived from the triangulation, 

 commencing with the latitude and meridian of Church Street, 

 Hobart Town, where Mr. Sprent took a series of observa- 

 tions, and calculated his latitude with great care, as will be 

 seen by his Eeport attached. Por the purpose of forming 

 an accurate map of the island, and fixing its geographical 

 position, the operations are proved to be exceedingly true, 

 and I believe the results equal any operation of the kind 

 in any part of the world; it being remembered that they are 

 not intended for the measurement of an element in the 

 dimensions or figure of the earth. 



The Bases, measured nearly one hundred miles asunder, 

 verify the operations with exceeding perfectness ; and though 

 it would be satisfactory to measure two other base lines on the 

 east and west coast, it cannot be considered necessary, as by 

 multiplying the calculations of the length of every line by 

 various chains of triangles branching from those directly 

 verified, any accidental error must be discovered, and a very 

 accurate mean taken, so that when the main triangulation is 

 completed, the main stations will be most accurately fixed 

 in position, both relatively and geographically, and the 

 inferior triangulation and filling in will be true in detail 

 under its control. It will be perceived that the latitudes of 



