Royal Society, 14)3 



The result of a coniparative trial made with the urine of the white- 

 headed Sea-Eagle, in one instance kept in darkness, in the other 

 exposed to bright sunshine for many successive days, afforded an 

 answer in the affirmative. Whilst the urine of the Sea-Eagle, con- 

 sisting chiefly of lithate of ammonia, kept in the dark, underwent 

 no change, that exposed to liglit was materially changed, most of 

 the lithate of ammonia had disappeared, its place was supplied by 

 oxalate of ammonia, the peculiar odour of guano was acquired, and 

 in part its brownish hue. 



jVom considering the composition of the lithic and oxalic acids, 

 the author infers, that in the conversion of the one into the other, 

 oxygen is absorbed ; and, in confirmation, he mentions that although 

 no change takes place when moist lithate of ammonia is exposed 

 alone to a temperature of about 212°, it is otherwise if so treated 

 when mixed with black oxide of manganese, in which case oxalate 

 of ammonia is formed, and also some brown colouring matter, not 

 unlike that of guano ; and this colouring matter, he supposes, may 

 appropriate to itself the excess of carbon and hydrogen, that is, 

 such proportions of these substances in the lithic acid as are more 

 than those required to form oxalic acid and ammonia. 



Having always found in the South American guano more distinct 

 traces of lithate of ammonia than in the African, he inquires 

 whether the difference may not be owing to different states of 

 atmosphere in the two regions ; — in the one, the clouded state of the 

 air impeding the sun's rays ; in the other, the usually unclouded 

 state interposing no obstacle to their full effect? He inquires too, 

 whether the circumstance of the comparatively rapid conversion of 

 lithic acid into the oxalic under the influence of light, as witnessed 

 in the experiment detailed, may not account for even recently 

 formed guano being destitute of lithate of ammonia ; and he men- 

 tions an example in point, namely, a specimen he had received from 

 the island of Ichabor being found with a large quantity of oxalate 

 of ammonia, to contain no lithate of ammonia, — a specimen described 

 as " having been scraped off a rock, where it was in a thin layer, 

 and much exposed to the sun." 



2. " An Account of the Newtonian Dial presented to the Royal 

 Society, in a letter to the President." By the Rev. Charles Turnor, 

 F.R.S 



The dial here described was taken down in the early part of the 

 present year from the south wall of the Manor-house of Wools- 

 thorpe, a hamlet to Colsterworth in the county of Lincoln, the 

 birth-place of Newton. It was marked on a large stone at the angle 

 of the building, and about six feet from the ground. The name of 

 Newton, with the exception of the first two letters, which have 

 been obliterated, are inscribed under the dial in wide and capital 

 letters. The gnomon has disappeared many years ago. 



3. " On the Non-coincidence of the Focus of the Photogenic Rays 

 with that of the Visual Rays of the Solar Spectrum," By M. A. 

 Claudet. Communicated by S. Hunter Christie, Esq., Sec. R.S., &c. 



After detailing the difficulties he had met with in obtaining per- 

 fect pictures when a lens, accurately corrected for spherical and 

 chromatic aberration, was employed in the Daguerreotype process, 



