Page:Proceedings of the Royal Society of London Vol 2.djvu/49

Rh account the author calls them binary, a term which applies to the numerous class of phenomena which he has observed by a great variety of combinations. He reckons as many as six kinds of rectilinear bands produced in his experiments which have not been noticed 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 spectra. 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. 



In the course of twenty-one years that have elapsed since the author'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 navigator 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,

Rh