Capt. Cullen on the Geology from Madras to Bellary. 435 



it. There is no spheroidical triangle ; there is no geodetical 

 line. The data consist of the latitudes, nearly equal, and the 

 azimuths, of two distant stations, yet sufficiently near for one to 

 be seen from the other. Now in the case of such distant sta- 

 tions, the observed azimuths are not the same with the azi- 

 muths in an imaginary geodetical line passing through the 

 stations. In this, and in other respects, there is great want 

 of precision and geometrical rigour in Dr. Tiarks' argumen- 

 tation. He has, in fact, brought forward nothing new either 

 in proof, or in elucidation of the problem of which he treats; 

 he has merely added the name of Dr. Tiarks to the other au- 

 thorities that have upheld the correctness of the method of 

 calculation in the Survey, which it is, nevertheless, just to cha- 

 racterize as the greatest delusion that has ever prevailed in 

 practical mathematics. I can add nothing more on this sub- 

 ject at present ; but on another occasion I will give another 

 solution of the same problem, more nearly allied in point of 

 form to the speculations of Dr. Tiarks, which will enable us 

 better to appreciate their merits. When the principles of the 

 problem are fully unfolded, we may then discuss the question, 

 Whether the calculations in the Survey are correct or not ? 

 Nov. 1828. J. Ivory. 



LXXII. Notice of the Geological Features of a Route from 

 Madras to Bellary, in April and May 1822. By Captain 

 W. Cullen, of the East India Company' s Artillery service. 



[Concluded from p. 363.] 

 HPHERE are two instances of the occurrence of a rather re- 

 -*- markable variety of quartzose rock in the course of the 

 preceding route, which have not been yet noticed, because it 

 differed very sensibly from any of the others, both in its co- 

 lour and composition, and appeared likewise to be altogether 

 independent of them. The first occurred on the west side of 

 the pass between Baukrapett and Cuddapah/occupying about 

 one mile of the route, and appearing to constitute the hills on 

 both sides. The lower end of the line of hills, crossed three 

 or four miles before reaching Nundialpett, were composed of 

 rock precisely similar, and were, I imagine, merely a continu- 

 ation of those forming the pass. I do not recollect any ap- 

 pearances of stratification in either case, although the course 

 of the range was conformable to the general direction. Per- 

 haps this rock rested on clay-slate, and may be considered as 

 merely one of those transitions, formerly alluded to, from sand- 



3 K 2 stone 



