1815.) | Magnetical Observations. 219° 
Comparison of Observations. 
1813. 1814, 1815... 
Morning ........| 24° 09’ 18” Ae 12! 53! 24° 16’ Ol 
April...... Noon .......- Sete} (242-21) 12 24 23. 53 24 27 Az 
VEU scp c.<-'> 24 15 25 24 15 30 24 17 48 
Morning ........ 24 12 02 24 13 #12 24 16 32 
DIAG iin: 0'0' 001s Noaniagiansa ts os! 5% 24 20 54 24 22 13 24 2T 03 
Evening....:..... 24 13 AT 24 16 14 24 19 12 
Morning ........ 24 12 35 24 13 #10 24 16 Il 
June...... Noame20-2.. Ent 24°22 17> | 24 22 48 24 27 18 
Evening ........ 24 16 04 24 16 29 24 19 40 
Morning ........ A 14 32 24 13 29 24 15 51 
July.. INGONIGS <icimaimalp's'4 24 23 04 24 23 AA 24 25 AS 
5 Evening...-......| 24 16 43 24 17 OO 24 19 Ag 
In deducing the mean of the observations in July, the morning 
_ and noon observations are rejected, on account of the great varia- 
tion. 
July 30.—The needle, after being steady for several weeks, 
vibrated 2’ 15”. The wind blew fresh from the north, and the 
needle has continued unsteady. 
, Between noon of the Ist July ; "4 
Rain fallen Between noon of the Ist Aue pi tan 
Evaporation during the same period .,........3°65 
Since the instrument was constructed with which these observa~ 
tions were made, Mr. George Dollond, of St. Paul’s Church Yard, 
has so much improved the construction, that the instrument which 
he now makes combines the advantages of a theodolite, transit, and 
equal altitude instrument and variation compass, and is equally 
portable with mine. 
a ee ee 
ArtTicLe XI. 
ANALysEs oF Books. 
1, Philosophical Transactions of the Royal Society of London for 
1815, Part L 
This volume contains the nine following papers :— 
1, Additional Observations on the O feat Paopertios and Struc- 
ture of heated Glass and unannealed Glass Drops. By David 
Brewster, LL.D. F.R.S. Edin. and F.A.S, Edin—In a former 
vaper the author had shown that glass, when heated, acted on light 
ike crystallized bodies; and that Prince Rupert’s drops possessed a 
similar property. On examining these drops carefully, lines were 
visible in them, forming imperfect cleavages, and rendering the 
