97 
' ■ Table (^Proportional Logarithms. 
' • EXAMPLE I. 
Kequired the Sun’s right ascension and declination, and the equation 
of time for noon at Edinburgh, on the 13th August 1819. 
O AR. noon, Green. 13th O** P.S Declination 14>° ti2' Equation 4‘"4a\9 
34th 9 32 47.5 . . 14 34 38 , . 4 30.6 
Daily var. of AR. &c. — - 3 46.2 P. L. 8039 . . 18 16 P. L. 1185 . 10.3 P.L. 3674 
Diff. longitude in time, 12 47 P.L. 2736 2736 . . . 2736 
Correction AR. &c. -f 2.0 . 1.0775 — 9" 44'"' . 3921 — 6"\5 , 6410 
or or 
— 9".7 — OM 
0 AR. noon, Greenwich, 9 32 47.5 Q Dec. N. Gr. 14 34 38.0 Equa. N. Gr. 4 30.6 
0AR. &c, N.atEdin.l3th,9 32 49.5 Declination 14 34 28.3 Equation 4 30.5 
EXAMPLE II. 
Required the corrections at Edinburgh for the same day, at 4^ 15*" P.M. 
Daily var. 0 AR. &c. as above. 3*" 46®.2 P. L. 8039 18' 16" P. L. 1185 i0®.3 P.L. 3674 
(4^ Id^q 12“ 8) =Green.,time, 4^* 27“.8 P. L. 7305 7305 7305 
Corrections, - -f 42". 1 ... 1.5344 ~3'24" . 8490 —1.9.1.0979 
0 AR. noon, Greenwich, 9 32 47.5 QDec.N. Gr.l4 34 38 Equa. N. Gr. 4 30.6 
0 AR. at 4^^ 15“ P. M. Edin. 9 33 29.6 ' 0 Dec. 14 31 14 Equation, 4 28.7 
Art. XVI . — On the Optical and General Properties of Tdba- 
sheer. By David Brewster, LL.D. F. R. S. Lond. & Ed. 
In the First Number of this Journal, we have already given a 
general account of the singular substance called Tabasheer, and 
of its inferiority in refracting power to all solid and fluid sub- 
stances hitherto examined. Since that article was published, 
the original paper has appeared in the Philosophical Transac- 
tions for 1819, Part II. ; and as the subject is of a popular na- 
ture, and easily understood by those who have but a moderate 
share of optical knowledge, we have thought it right to present 
the reader with an abridged account of it. 
Tabasheer readily imbibes all the volatile and fat oils, and in- 
deed all the fluids that I have tried. The essential oils are 
quickly absorbed, and, with the exception of oil of cassia, are 
as quickly evaporated, while the fat oils are slowly drawn in 
and remain a long time in its pores ; and in all these cases an 
yOL. II. NO. 3. JANUARY 1820. 
G 
