—— 
TRANSACTIONS OF THE SECTIONS. 51 
reputed riches... Manoa, the capital of El Dorado, was said to be built on a large 
lake, which Hondius first represented in his map of Guiana as 200 leagues long and 
forty broad, assigning as its locality the isthmus between the Rupununi and Rio 
Branco ; subsequent geographers retained the Laguna Parima, or Mar Blanco, but 
varied its locality; and although Humboldt, by reasoning founded upon personal 
experience and the inspection of every document relating to the country, asserted 
that such a lake could have no real existence, yet within the last few years maps 
have been published upon which the lake still figures. At the time Humboldt pub- 
lished his Atlas, the regions north of the Amazon, three times as large as Spain, were 
unknown. I[t was this country which the author had been engaged in exploring since 
1835, and the large maps which illustrated his paper proved the correctness of Hum- 
boldt’s judgement. The fable of the “ Mar Blanco” had doubtless arisen from the an- 
nual inundations of the vast savannahs between the Rupununi and Rio Branco and the 
Pacaraima Mountains and the thick forests of Essequibo, covering an extent of 14,000 
square miles. These might once have formed an inland lake, but not within the histo- 
ric period. The author then gave a sketch of the geography of Guiana, which, 
although the largest British colony in South America, was so little known as to be 
sometimes spoken of as an island. The province is bounded in its widest extent by 
the rivers Amazon and Orinoco, and comprises an area of 690,000 square miles ; the 
Casiquiare canal connects the Orinoco with the Rio Negro and the Amazon; so that, 
in this way, the province may be circumnavigated. The fertility of the country is 
surprising to those accustomed only to the vegetation of the temperate zone; but 
the author gives it as his opinion, that no natives of the north of Europe could endure 
the climate as labourers in the open air. The rivers of Guiana, aided by short over- 
land portages, aftord inland communication with Monte Video at the mouth of the 
La Plata, with Cuzio, Lima, and Santa Fé de Bogota. The Parime and Pacaraima 
Mountains separate the fertile plains of the Lower Orinoco from those of the Rio 
Negro and the Amazon; the loftiest summits are in the most southern ranges, and 
in those most northerly. Maravacca, near the Orinoco, rises to 11,000 feet, and 
Roraima, the culminating point of the Pacaraima Mountains, is 8000 feet above the 
sea; they are composed of the older red sandstone, and exhibit mural cliffs 1000 and 
1600 feet high. From the walls of the latter mountains the river Kamaiba precipi- 
tates itself, in a cascade of nearly 1500 feet, surpassing the Cascade de Gavarnie in 
the Pyrenees, which is 1266 feet. In the neighbourhood of these mural mountains, 
porphyry, jasper and rock crystals are found. 
Notice and Drawings of the Footprints of various Animals on the New Red 
Sandstone of Corncockle Muir. By H. E. Srrickxuanp, F.G.S. 
On Nodules, apparently Coprolitic, from the Red Crag, London Clay, 
and Greensand. By Professor Henstow. 
The supply of phosphate of lime used in agriculture, and hitherto obtained from 
bones, having of late years become insufficient, Dr. Daubeny had been induced to 
visit Spain, in order to learn whether this deficiency could be supplied from the de- 
posit of phosphorite in Estremadura. From his report, there appeared to be diffi- 
culty attending the project ; but so important was it deemed, that a second expedi- 
tion had been made for the sake of further investigation. In October 1843, Prof. 
Henslow had called attention to the occurrence of phosphate of lime in pebbly beds 
‘of the red crag at Felixstow, in Suffolk; these nodules, though extremely hard, pre~ 
sented external indications of an animal origin, and yielded, upon analysis, 56 per 
cent. of phosphate of lime. Mr, Brown of Stanway, had subsequently obtained 
several analyses of these pebbles, and also of similar nodules obtained from the London 
clay in the vicinity of Euston-square, and found the same amount of phosphate of 
lime, viz. 50 or 60 per cent. in each. The crag pebbles occasionally contain re- 
mains of small crabs and fish like those in the London clay, leading Mr. Brown to 
the conclusion that they were derived from the destruction of certain beds of that 
_ ‘series. The crag nodules were so abundant, that a gentleman had obtained two tons 
_ “of them—which, after being prepared, were found upon analysis to contain 53 per 
