Dr Brewster on a Monocltromatk Lamp 
Tab. VI. — Continued. 
Names of Places. 
Year of 
Observa- 
tion. 
Magne- 
tic Va- 
riation. 
Names of Places. 
Year of 
Observa- 
tion. 
Magne- 
tic Va- 
riation. 
Malta, - 
Minorca, C. Mola, 
Padua, - 
Rome, - 
1694| 
1708 ^ 
1733 
1725) 
1730] 
1770 
1670 
1681 
9°15'W. 
9 45 
10 25 
14 34 
13 0 
16 20 
2 15 
5 0 
Rome, 
1695 
1730 
1782 
1783 
1784 
1785 
1786 
1787 
1788 
7°30'W. 
11 0 
16 49 
16 49 
16 54 
17 0 
17 4 
17 7 
17 12 
Table VII. Containing the Variation of the Needle, as observed 
in Turhey in Europe.i 
Names of Places. 
Year of 
Observa- 
tion. 
Magne- 
tic Va- 
riation. 
Names of Places. 
Year of 
Observa- 
tion. 
Magne- 
tic Va- 
riation. 
Akiermann, 
Bender, 
Bucharest, 
Constantinople, 
1771 
1772 
1772 
1600 
1625 
1694| 
9°25'W. 
9 45 
11 86 
0 0 
2 0 
9 0 
12 0 
Ofen, - ^ 
1 
1781 
1783 
1782 
1784 
1785 
1787 
1788 
16? 45' W- 
15 58 
15 36 
15 40 
15 48 
16 26 
16 36 
( To he Continued.) 
Art. XVIII. — Description of a Monochromatic Lamp for Micro- 
scopical and other purposes <^c. By David BrewsteKj 
L. Ij. D. & Sec. R. S.5 &c. 
In a Paper on Vision through coloured Glasses -f, which I had 
lately the honour of submitting to the Society, I pointed out 
the advantages of coloured media in Microscopical and Teles- 
copical observations. Having experienced the great utility of 
Green and Red lenses, in developing vegetable structures that 
required to be examined with high powers, I was anxious to 
derive from this new principle all the advantages which it ap- 
peared to possess. In attempting to do this, it became necessary 
* Abridged from the Edinburgh Transactions^ vol. ix. p. 433. 
.‘f See this Journal, vol. VI, p. 102. 
