1834.] Errors of the Madras Mural Circle. 403 



history of the antediluvial or postdiluvial tenants of the Nerbudda fossil 

 bason : for it is by no means clearly established yet to what epoch the 

 debris belong. We have to learn whether the gravelly bresciaeverwrtefer- 

 lies the alluvium, or any of the regular deposits of the valley ? or whether 

 it merely fills up crevices and angles at the foot of cliffs, from which the 

 trickling of springs charged with carbonate of lime might be derived. 

 I have before remarked, that the conglomerate matrix contains rolled 

 pebbles of quartz, felspar, and basalt, and therefore its formation is 

 much subsequent to the deposit of the flcetz trap, the most recent of the 

 regular rock deposits of the Sagar district. The trap itself is of course 

 anterior to the black alluvium of the Nerbudda valley, which is princi- 

 pally formed from its detritus. Is the brescia contemporaneous with 

 this black alluvium or subsequent thereto ? is the question to be solved. 



Professor Buckland was unable to determine whether the Ava bones 

 of mastodons, hippopotami, alligators, &c, were referrible to "the most 

 recent marine sediments of the tertiary formation, like the elephant of 

 the Norfolk crag ; or to the antediluvian fresh-water deposits analogous 

 to those of the Val d'Arno ; or lastly to the diluvial accumulations more 

 modern than either of these formations ;" but he inclined to refer them 

 to the latter, because of the rolled gravel cemented to them, which re- 

 sembled the matrix of many of the European mammalian fossils. So far 

 the Ava fossils agree with those of central India, but they differ in being 

 mineralized (at least such as we have lately received from Col. Burney) 

 with hydrate of iron instead of carbonate of lime. Capt. Macleod how- 

 ever informs me, that such as were calcareous were rejected by Col. 

 B., not being considered to be thoroughly fossilized. 



But I must now quit this interesting subject, hoping shortly to recur 

 to it, armed with additional facts from Sergt. E. Dean, whose hippopo- 

 tamus' tooth and other curious and new fragments from the Jamna were 

 lately submitted to the Society, and whose notes are only withheld from 

 publication in expectation of further information from the same source. 



VI. — Determination of the Errors of Division of the Mural Circle at the 



Madras Observatory, by T. G. Taylor, Esq. H. C. Astronomer, Fort 



St. George. 



[In a letter to the Editor.] 



I beg to trouble you with the result of some observations which I 

 lately made with a view of determining the amount of error of division 

 of the Madras Mural Circle. 



Hitherto (with but one exeption I believe*) it has been the 

 practice of astronomers to avoid the effect of error of division by 



* Professor Bessel. 

 2 f2 



