17 



account the author calls them binary, a term which applies to the 

 numerous class of phenomena which he has observed by a great va- 

 riety of combinations. He reckons as many as six kinds of rectili- 

 near bands produced in his experiments which have not been no- 

 ticed by any other writer. 



In order to ascertain what effect the presence of air might have 

 on these phenomena, the author repeated some of his experiments 

 in vacuo, and found that the removal of the air had no perceptible 

 effect. 



Even the interposition of water between the surfaces appears to 

 him to diminish but little the brilliancy of the colours. Nitric acid 

 has more effect ; and in fluids of greater density, as olive oil, the 

 whole class of phenomena disappear. 



It appears somewhat strange, says Mr. Knox, that Newton 

 should have attributed the coloured rings to a plate of air and to 

 supposititious fits of easy reflection and refraction, when a cause more 

 obvious was at hand ; namely, the interference of the reflecting and 

 refracting strata diffused over the contiguous surfaces : for it may be 

 supposed, that when a ray passing out of glass into air is interrupted 

 and receives a new impulse by the influence of a second refracting 

 medium, these contrary impulses may be repeated many times, and 

 by repeated vibration may affect the rays according to their different 

 refrangibility, so as to separate them into differently coloured spec- 

 tra. He therefore thinks it highly probable, that by this compound 

 action and reaction between the strata and light, and between the 

 rays of light themselves, all the various phenomena are produced, 

 although from their extreme minuteness an accurate knowledge of 

 the mode of operation is not to be expected. 



Some farther Observations on the Current that often prevails to the 

 Westward of the Stilly Islands. By James Rennell, Esq. F.R.S. 

 Read April 13, 1815. [Phil. Trans. 1815,;?. 182.] 



In the course of twenty-one years that have elapsed since the au- 

 thor's original communication on this subject was published in our 

 Transactions, he has collected many new instances of the effects of 

 the current, tending to confirm the general observations respecting 

 its course from Cape Finisterre to Scilly, and affording clearer proof 

 of the strength of the stream than any evidence that he could adduce 

 on the former occasion. The first fact relates to its commencement 

 in an easterly direction, toward Cape Finisterre, from a distance of 

 at least fifty-three leagues, in the instance of the Earl Cornwallis 

 Indiaman, which drifted in that direction at the rate of twenty-six 

 miles per day. 



In the second instance, a bottle thrown out by a Danish naviga- 

 tor was carried in a direction E. by S. to Cape Ortegal, a distance of 

 sixty-four leagues. 



A third fact was communicated to the author by Admiral Knight, 

 VOL. n. c 



