1^1.] Nmi) Clinometer. — Red Snow. '43 



Article VI^ 

 Description of a new Clinometer. By S. P. Pratt." 

 k . !\ (With a Plate.) : p 



;^^^ ,(To the Editor of the Annals of Philosophy.) 



Isife, Tottenham, Dec. A^'iO. 



► , I SEND you a drawing (PI. II.) of a simple instrument which 

 .jf'have had some time in use for determinmg the dip of strata,: 

 it consists of a brass ruler, of 12 inches by f of an inch in breadtH, 

 closing upon an hinge, and covering, when closed, an arch 

 drawn from the centre of the hinge, and divided into 90 degrees 

 on the same side ; near one extremity of the ruler a small spirit 

 level is inserted truly horizontal, with its edge — the applica- 

 tion is obvious. The ruler being closed, with the level upper- 

 most, is placed parallel to, or upon any projecting edge of, the 

 strata to be examined, and then gradually opened until the 

 level becomes horizontal ; the bisection of the arch near the 

 hinge of the ruler will give the angle formed by its two legs, and 

 consequently the inclination of the strata with the horizon. 



I am, Sir, yours, S. P. Pratt. 



Note.— The simplicity of this instrument appears strongly to 

 recommend it. It is made and kept for sale by Mr. Bate, 

 Poultry. Ed. 



Article VII. 



On Red Snoiv. By Dr. Henderson. 

 (To the Editor of the Annals of Philosophy.) 



DEAR SIR, Curzon-strcet, Dec. 9, \S20. 



In the several accounts which were given of the red snmo 

 found in Baffin's Bay, I do not recollect that any one has 

 adverted to the fact of this phenomenon being familiar to the 

 ancients. While I was lately turning over the pages of the 

 indefatigable Pliny, for a very different object, I stumbled upon 

 a passage (lib. xi. c. 35) where he mentions that snow turns red 

 hy 2ige—** ipsa nix vetastate rubescit.'' Nor is the cause thus 



-assigned for the colour by any means inconsistent with the best 

 analyses of the red snow as brought to this country in a liquid 

 form; for it is evident that if this variation of the colour of the 

 Enow on particular spots be the result of the formation of a lichen 



at byssus on its surface, it can only be on the old snow that 



iBUch vegetation will occur. 1 remain, dear Sir, 



Your most obedient servant, 



M. H&NBERSOiU 



