90 



Meteorology, 



variations of temperature have increased, or that a disproportion of 

 temperature between the water and air has increased, or that the 

 Thames has diminished in depth. It is my behef that the last has 

 occurred, partly from the natural rise of all embanked river beds, and 

 partly from the effect of Waterloo Bridge. This bridge is unhappily placed 

 near a bend of the river, and it is to be feared that the allignment of the 

 arches of the other bridge, and the course of the current, have not been 

 duly considered. The only remedy is to narrow the channel, so as to 

 increase its depth, upon some such plan as Colonel Trench's. The quays 

 of the insignificant Seine are open, the Thames is inaccessible. It is, 

 however, very dubious whether that great work would pay as a commer- 

 cial speculation. {Courier ^ Nov. 20. 1827.) 



On the Crystallisation of Snow. — Sir, Having been so fortunate as to 

 meet with the snow crystals in great plenty this winter, I cannot help 

 thinking that, as I believe they are not often seen in this country, it may 

 be acceptable to some of your readers to have the following short account 

 of them : — On the 4th of this month (Feb. 1830.), and for some days after, 

 the thermometer standing at about 22°, and the wind from the E.N.E. 

 nearly all the snow that fell was of that beautiful stellated form, called by 

 Scoresby, in his work on the Arctic Regions (vol. i. p. 477.), the " lamellar 

 stelliform crystals." They consist mostly of six points, radiating from a 

 centre, forming with each other, at that centre, angles of 60°, and having 

 commonly additional ramifications on the primary ones, in the same plane 

 with them, and forming angles of 60° with the primaries, as in the following 

 figures {Jig. 37.), of which the form b was the most common, and after that 



c and d. e and / were but seldom seen, and g I met with but once. 

 The last three appear to be formed by the obliteration of the alternate 

 rays, so as to form angles of 120° instead of 60°; the additional rami- 

 fications still forming angles of 60°, with the primaries, hy i, and k, 

 which I did not see myself, but which were communicated to me by a friend, 

 appear to be crystals in a progressive state of formation. The size of the 

 crystals varied from one eighth to one third of an inch in diameter. It 

 appears from Scoreby's table (vol. i. p. 433.), that the time when the 

 greatest quantity of crystals fell was when the thermometer stood between 

 16° and 22°, and the wind was N.E. or N.N.E. ; which nearly corresponds 

 with what was observed here. Th& forms observed do not exactly agr^e 



