Mr. F. Baily on the Circular Micrometer. ] 77 



some degree giddy It was not felt by any one who was on 

 horseback; and this was the case with several of our officers 

 li-very one, however, who was on the ground felt it to be verv 

 alarming. ° vciy 



The duration of it was not measured by any one, but I 

 hmk it lasted about two minutes. It was at first slight, and 

 towards its termination the motion became less and ?ess via- 



«£ T^ ^ ?° aCC ° UntS f '* from neighbouring towns; 



much „ T f t0 l UPP T * haS n0t been so ™ le »t as to do 

 much mischief in other places. 



This country, Kattiwar, is rocky and rugged. The rock 



trant^T^ "^^^ ^ volcanic nature, unless the 

 trap be considered such.-I now have the honour to remain, 

 Sir, your very obedient servant, 



(Signed) G. A. Stuart, 

 Assistant Surgeon, 1st Light Cavalry. 



XXXI. On the Circular Micrometer. By F. Baily, Esq. 



F.R.S. 



fHE circular micrometer is an instrument which has been, 



stm £ dT&r'T?' mu< ? used on the ««*«* - " 



still held in high and deserved estimation there b v astrono- 

 mers of the first rank. From the simplicity of it7construc- 

 tZ^Tthl^ ^ With / hich * may be Led in^posl 



and tS^ST' > - S freqUen% Prefen ' ed ' even »pubUc 

 and national observatories, to micrometers of a more complex 



of tl^'stlr Ch M qUh ' e t0 h ? adJUSt6d t0 the ^torLTS 



lummated on ^ TT"* ^ ? n ° M0Mri ^ for its bei "g *" 

 luminated; on which account it is peculiarly adapted to the 



observation of comets and small stars: and it is tadeed to 



these two classes of the heavenly bodies, that its a ppUoSonS 



now principally confined ; although som'e astronomers of gea 



eminence have considered that it is capable of equal accJCy 



to the wire micrometers. To voyagers and others, who are 



travelling for the improvement of astronomy and ge^raX 



size (it be ng not much larger than a shilling) renders it very 



fonn o ^ 7 A? blllty l ° mjUry - ° n this aCCOUIlt ifc ought to 

 form a part of the apparatus of every person travelling under 

 the circumstances above alluded to. ° 



Astronomy « indeed more indebted to this little instru- 

 vol. 63. No. 311. March 1824. Z mo „* 



ment 



