380 Royal Society. 



= r, the above expression changes nothing but its sign ; 

 which, therefore, upon transcendental grounds, it is easy to 

 see is of one name or another, according as^? is odd or even. 



In the original paper, I asserted this theorem only for the 

 case of p = or q = 0. 



University College, London, Oct. 29, 1840. 



LVIII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



June 18/ I ^HE following letter was read from G. Go Anson, Esq., 

 1840. JL addressed to the President, enclosing a specimen of a 

 deposit with which nine acres of land near Exeter, belonging to Lord 

 Radnor, had been covered after the subsidence of a flood, and which 

 was sent by H.R.H. Prince Albert, F.R.S. :— 



"Buckingham Palace, June 8, 1840. 

 " My dear Lord, 

 " His Royal Highness Prince Albert has commanded me to for- 

 ward to you the enclosed specimen, which has been sent up to His 

 Royal Highness from Lord Radnor's place near Exeter, where nine 

 acres of land were covered with this curious substance after a flood 

 had subsided. His Royal Highness thinks it very probable that the 

 subject may already have been brought before the Royal Society, but 

 in case it should not have been, he sends the accompanying packet. 

 It is said that a good deal of it has been applied to the purpose of 

 making waistcoats for poor people. 

 " Believe me, 



" My dear Lord, 



" Yours very faithfully, 



" G. G. Anson." 

 " The Marquis of Northampton, President of the Royal Society." 



The following description of the specimen referred to in the letter, 

 drawn up by John Lindley, Ph. D. F.R.S. , was also read : 



" Description of the Specimen referred to in the preceding letter." 

 By John Lindley, Ph. D., F.R.S. 



The plant which overran Lord Radnor's land is the Conferva crispa 

 of Dill wy n, which is said to be the Conferva fiuviatilis of Linnaeus. 

 The species inhabits fresh water, and multiplies with great rapidity, 

 forming entangled strata. The green portion is the Conferva in its 

 young state, the white portion is the plant old and bleached. The 

 whole mass consists of articulated filaments, among which are frag- 

 ments of grass-leaves. 



The following papers were then read, or their titles announced : — 



1. An Account of Experiments on the Reflecting Telescope. By 

 the Right Hon. Lord Oxmantown, F.R.S. 



This paper enters minutely into the details of the experiments, of 

 the precautions requisite to ensure success, and of the manipulations 



