Royal Society. 311 
district, to have been prodigiously lifted, and to be dena- 
dated (or abrupted as Dr. W. Richardson has termed similar 
operations in Ireland, in the Phil. Trans. 1800, see our 
33d vol. p. 114,) or have a very great thickness of the 
upper strata stripped from off them, and gone. That within 
this tract other 4aults partly surround a second tract, which 
is more raised than the first ; and within this again, another 
tract of limestones and toadstones in Derbyshire and Staf- 
fordshire is partly surrounded by other faults, and still more 
raised and proportionally denudated, so as, in the opinion of 
the writer, to exhibit lower strata in the British series, than 
perhaps any other parts of these islands exhibit. The 
combined effect of these successive lifts, and the general 
denudation, has been, to exhibit at the southern end of the 
Weaver Hills in Staffordshire, a far greater vertical, de- 
rangement of the strata or fault, than has hitherto been 
mentioned by any writer. A smallerraised tract, similar to 
the inner one of the above, is also described, on which the 
town of Bakewell is situatedy and it 16 shown, how the 
rise of the western edye of this tract and the excavation of 
the valleys for the Wve, the Lathkil, and the Bradford ri- 
Vers, occasions the Ist toadstone under the Ist limestone 
rock (which forms the gencral surface) to be locally laid 
bare in these yallevs. The great number of names of places 
and of strata mentioned in this letter, prevents our giving 
a more detailed account of its contents. From the minute- 
ness with which they are described, it will, we trust, here- 
after prove interesting to geological readers. 
April 4.—A long paper, by Mr. Jordan, on light and the 
coloured rings of thin plates, was read, in which the au- 
thor, after repeating his former objection to the supposed 
theory of Newton, that light has fits of easy transmission, 
refuted the theories lately proposed in the Philosophical 
Transactions ; asserted his claim to priority in this inquiry ; 
examined and pointed out the inadequacy of what he called 
the bow-theory ; declared his opinion that, contrary to the 
ideas of Newion, white light is not a compound, but de- 
rives its colours from the objects by which it is refracted ; 
and concluded with promising anew and satisfactory theory 
of the phanomena of coloured rings in thin plates, which 
he is about to bring forward immediately. He has pur- 
sued these researches for a series of years, published the 
result of some of them in the Philosophical Transactions for 
3799, and has since greatly extended and improved them. 
The Society then adjourned, in consequence of the Easter 
festival, till Thursday, April 25th, when part of an ingenious 
papers was read on the measurement of the head, by baie 
U4 ell, 
