390 Magnetical Observations. (May, 
ARTICLE X. 
Magnetical Observations. By Col. Beaufoy, F.R.S. 
(To Dr. Thomson.) 
MY DEAR SIR, Bushey Heath, April 18, 1817. 
ALLow me to mention, these observations were made with the - 
same instrument and needles as in the years 1813, 14, and 153 
but the base of the instrument, instead of resting on a piece of 
mahogany, is now placed on a brass triangular stand, through the 
angles of which are inserted the three mill-headed screws for level- 
ling it. By this improvement the instrument, when once levelled, re~ 
tains its horizontal position, the wooden stand being liable to warp. 
The object glass also can now be adjusted for different distances. 
One needle is a very slender parallelopipedon, and weighs 51 gr. ; 
the other is of a cylindrical form, terminating at each extremity 
with a cone, and weighs 63 gr. The increase of weight in the 
needles is owing to the new agates which have been put in. 
In the subjoined meteorological table Fahrenheit’s thermometer 
is used, and M. de Luc’s hygrometer. ‘The velocity of the wind 
is determined by taking the mean of the times it blew three different 
miles, and then reducing that mean to feet per second. The diree- 
tion of the wind is counted from the true points of the compass. 
J remain, my dear Sir, yours very sincerely, 
Mark Bravuroy. 
Bushey Heath, near Stanmore. 
Latitude 51° 37/42” North. Longitude west in time, 1/ 20-7”, 
Magnetical Observations, 1817. — Variation West. 
Morning Observ. Noon Observ. Evening Observ. 
Month. 
Hour. | Variation. | Hour. | Variation, | Hour. | Variation. 
April 1} 8h 45’) 24° 33’ 37") Ih 45’) 240 43' 14”) 6h 20'| 24° 33/ 54” 
2| 8 42) 24 32 25) 1 45 | 24 47 09 | 6 20| 24 37 08 
3} 8 48] 24 31 06; 1 49 | 24 50 02] 6 18] 24 37 20 
4) 8 49) 24 32 O1;] 1 50| 24 48 32] 6 20} 24 41 16 
5] 8 47] 24 31 41] I 50/24 49 08| 6 45} 24 36 44 
6| 8 45] 24 35 39| 1 45 | 24 46 53} 6 40 | 24 38 04 
7} 8 50] 24 33 53] 1 55] 24 46 29| 6 40] 24 37 06 
8| 8 45/24 35 45! 1 40| 24 44 50] 6 40| 24. 36 48 
9| 8 45] 24 3T 25} 1 45/24 42 00} 6 30) 24 33 43 
10; 8 40} 24 32 23] 1 40/24 44 55| 6 40 24 35 2 
11; 8 40/24 31 06/ 1 50/24 43 98;— —|— — — 
12} 8 45] 24 30 OT] 1 45/24 44 02] 6 45) 24 35 39 
13} 8 35} 24 30 11] 1 40/ 24 45 O01] 6 45 | 24 35 40 
14, 8 45/24 30 19] 1 50} 24 45 46] 6 50] 24 35 14 
15) 8 45 | 24 30 55| 1 45 | 24 45 49| 6 45 | 24 34 36 
16) 8 45/24 29 03] 1 40/| 24 44 30| 6 45/24 35 34 
17) 8 45| 24 29 36] 1 45 | 24 43 38| 6 45] 24 35 43 
