6 NATURAL APPEARANCES 



Obs. 6. The tracks which have been now defcribed, are not 

 ftraight lines, but have all more or lefs of a regular circular na- 

 ture in them ; that is to fay, they are fegments of circular fi- 

 gures, and only approach to the appearance of right lines, in 

 proportion as the figure of which they are the fegments is 

 large, or the fegment fmall % and in thofe refpecls there appears 

 to be great variety. There is, however, one appearance which, 

 at nrft fight, might impofe upon an obfervator, and deftroy the 

 generality of this obfervation. It is an inflance or two that oc- 

 cur of a continued line in thofe tracks ; but, in this cafe, the 

 line appears to be made up of feveral fegments, each of which 

 ought to be confidered by itfelf ; confequently, here will be ac- 

 knowledged the operation of the fame general principle by 

 which, in thofe appearances, a regular figure is produced, and 

 that this figure is in its nature circular. 



Obs. 7. The production of thofe tracks being fucceffive in 

 its nature, or operating in different places at different periods of 

 time, fuggefts another fubjecl of enquiry, viz. How far any re- 

 gularity, or a certain order, may be obferved alfo with regard 

 to this operation, as well as with regard to that by which the 

 figure is produced ? And this, from obfervation, I think, is de- 

 termined in the affirmative, fo far as, from all the obfervations 

 I have made, this progrefs feems always to have proceeded in 

 the direction of a. line, drawn from the centre, bifecling the 

 fegment ; that is to fay, thofe portions of concentric circles 

 are never infcribed, but always circumfcribed ; and, for this 

 reafon, it will appear, that thofe circles, of which fegments are 

 exhibited to our obfervation, muft be increaiing, and not di- 

 miniming, in their diameter. 



Having thus given an account of what was concluded from 

 the firft feafon of thofe obfervations, before proceeding to give 

 the continuation of their hiftory, it may be proper to obferve, 

 that an unfuccefsful attempt was once made to inveftigate the 



caufe, 



