ON THE OBLIQUITY OF THE ECLIPTIC. 193 



2. No observation of this kind has been, I believe, made in India., 

 (or at least given to the public) since Mr. Le Gentil visited P on di cherry , 

 in the years 176S-9. Nor do I think that any instrument of sufficient 

 power for that purpose had reached this country, until the government of 

 Fort St. George were pleased to purchase and intrust to my hands a cir- 

 cular instrument made by Gary, in the year 1807; which, being used with 

 proper attention, and some degree of skill, proved perfectly adequate to 

 the purpose. This will appear from the consistency and regularity of the 

 observations and results which form the subject of this paper. 



3. This instrument being intended for astronomical and geographical 

 observations, in all cases where angular distances may be the object, is on 

 that account somewhat complex. But I shall confine my description to 

 its means and powers for taking altitudes. 



4. The vertical circle is 18 inches in diameter, and is divided in a 

 masterly manner on the limb to fifteen minutes. In order to read the 

 intermediate parts there are two microscopes, fixed horizontally on 

 Brachia?, consisting of an horizontal, and an oblique ladder bar, meeting 

 at an angle somewhat acute, to where the microscope is suspended, the 

 other ends being screwed against the conic pillar which supports the axis 

 of the circle on that side. 



5. This mode of suspending the microscope (though perhaps suf- 

 ficient for northern countries) is rather defective for tropical climates; 

 for after using this instrument upwards of ten months, I perceived the 

 absolute impossibility of trusting to the level alone for very fine observa- 

 tions, and saw the necessity of a constant reference to an horizontal mark 

 placed at a convenient distance, for accurate results. This irregularity 

 compelled me to reject the solstitial observations which I had taken in 



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