330 Analysis of Scientific Books. 



parallax appears to me to be this : in proportion as instruments 

 have been imperfect in their construction, they have misled ob- 

 servers into the belief of the existence of sensible parallax. This 

 has happened in Italy, to astronomers of the very first reputation. 

 The Dublin instrument is superior to any of a similar construction 

 on the continent ; and, accordingly, it shews a much less parallax 

 than the Italian astronomers imagined they had detected. Con- 

 ceiving that I have established beyond a doubt, that the Greenwich 

 instrument approaches still nearer to perfection, I can come to no 

 other conclusion, than that this is the reason why it discovers no 

 parallax at all." 



S. Observations on the Heights of Places in the Trigonometrical Survey 

 of Great Britain, and upon the Latitude of Arbury Hill. By B. Bca- 

 van, Esq. Communicated by Sir H. Davy, Bt., P.R.S. 



By levelling to the Grand Junction and other canals, the author 

 found the country to the north of Arbury Station, suddenly to fall 

 about four hundred feet, and to continue thus depressed for ten 

 miles. Such a defect of matter induced him to suppose a south- 

 ward deflection of the plumb-lime, and by calculating the latitude 

 of Arbury from that of Blenheim, as determined by previous obser- 

 vation, he found it five seconds less than shewn by the zenith 

 sector. 



9. On some Fossil Bones discovered in Caverns in the Limestone Quar- 

 ries of Oreston, by J. Whidbey, Esq., F.R.S. In a Letter addressed to 

 John Barrow, Esq., F.R.S. To which is added a Description of the 

 Bones. By Mr. W. Gift, Conservator of the Museum of the College 

 of Surgeons. 



We owe to Mr. Whidbey the important geological fact of the ex- 

 istence of cavities containing bones, in the solid secondary lime- 

 stone of Plymouth, which cavities exhibit no traces whatever of 

 any external outlet. In his description of the cavern containing 

 the bones of the rhinoceros, printed in the Philosophical Transac- 

 tions for 1817, he particularly insists upon the uniform solidity of 

 the surrounding rock. Sir E. Home tells us that Mr. Whidbey " saw 

 no possibility of the cavern having had any external communica- 

 tion," and this singular and important circumstance is further veri- 

 fied as follows. " As in the contract for quarrying there are two 

 prices, one for rock, and another for clay, earth, and rubbish, and 

 two officers attend, one for the crown, and the other on the part of 

 the contractors, who measure the contents of all caverns that contain 

 clay or other soft materials, it is only necessary to mention that 

 these officers state, that the rock surrounding the cavern was equally 





