128 



The specific gravity of the spring-felled alburnum was 0'666 ; that 

 of the winter-felled, 0'565. Equal blocks of each alburnum were 

 cleaved into thin pieces ; and, when perfectly dry, suspended in a 

 damp room for ten days. One thousand grains of the alburnum of 

 the spring-felled tree gained 162 grains, and of the winter-felled 145; 

 so that there is an obvious difference in the properties of the two ; 

 and Mr. Knight doubts not, by taking the bark off in the spring, and 

 not felling the tree till winter, that the timber would be materially 

 improved. He also thinks that these observations are applicable to 

 the heart wood as well as to the alburnum, though he has not at 

 present any very conclusive evidence to offer on that subject. 



On the Mode of Formation of the Canal for containing the Spinal 

 Marrow, and on the Form of the Fins (if they deserve that name) of 

 the Protco-Saurus. By Sir Everard Home, Bart. V.P.R.S. Read 

 May 4, 1820. [Phil. Trans. 1820, p. 159.] 



The structure of the vertebrae of the Proteo-saurus is intermediate 

 between that of the lizard tribe and cartilaginous fishes, and they have 

 so close a resemblance to the vertebrae of the shark, as often to have 

 been mistaken for them. They are composed of bone, and have a 

 body and canal for the spinal marrow, and a process for the attach- 

 ment of muscles ; but the body is made up of one piece, while the 

 spinal process, and two lateral branches which belong to it, are made 

 up of another ; between these there is no union but a species of joint 

 peculiar to themselves ; the hole in the middle thus formed appears 

 unusually small. 



In the specimen from which the above description is taken, there 

 is also a fore foot, paddle, or fin, 'for it is difficult to say which it 

 should be called, and which, though not quite perfect, is more so 

 than in any other extant specimen. It presents nothing like the 

 thumb or claw for laying hold, which distinguishes the animals that 

 occasionally inhabit the sea, and come ashore to lay eggs or deposit 

 young. If it be called a fin, it is to be understood as made up of 

 bony materials, the joints of which are extremely numerous, so that 

 it may possibly perform the same office. 



An illustrative drawing accompanies this paper. 



Some Experiments on the Fungi which constitute the Colouring Matter 

 of the Red Snow discovered in Baffin's Bay. By Francis Bauer, Esq. 

 F.L.S. In a Letter addressed to the Right Hon. Sir Joseph Banks, 

 Bart. G.C.B. P.R.S. #e. %c. Read May 11, 1820. [Phil. Trans. 

 1820, p. 165.] 



To ascertain whether the fungi mentioned in the title of this pa- 

 per vegetate in the snow, Mr. Bauer put a small portion of them into 

 a phial filled with compressed snow, and placed in the open air in a 

 N. W. aspect. In fifty-two hours they had formed a red sediment ; 

 and the snow being thawed the water was poured off, and a fresh 



