TEANSPAEENCY OF VAEIOUS BODIES. 
865 
Table I. — Diactinic Power of Solids, 
Name of substance. 
THclmess, in inches. 
Termination 
of spectrum. 
Eelative 
lengths of 
spectra. 
Remarks. 
Ice 
about 0*5 
170-5 
74-0 
Diamond* (1) 
0-032 
155-5 
59-0 
Diamond (w) 
0-017 
139-5 
62-0 
Diamond (A) 
0-182 
113-3 
19-0 
Sapphire (24) 
0-13 
116-0 
19-5 
Sapphire (B) 
0-093 
112-0 
15-5 
Faint bluish tinge. 
Sapphire (n) 
0-12 
111-0 
14-5 
Quartz 
0-16 
170-3 
74-0 
With quartz-train. 
White Topaz 
0-19 
162-0 
65-5 
Faint image of spectrum. 
Mica 
0-007 
114-3 
18-0 
Oil of Vitriol 
0-73 
160-5 
64-0 
Sulphate of Lime (solid) 
about 0-3 
155-5 
59-0 
Sulphate of Baryta (solid) ... 
about 0-4 
154-5 
58-0 
Sulphate of Magnesia (solid) . 
0-34 
158-0 
61-5 
Sulphate of Potash 
Sat. soln. 0 75 in. 
159-5 
63-0 
Sulphate of Soda 
159-5 
63-0 
Sulphate of Ammonia 
yy 
143-5? 
49 - 0 ? 
Sulphate of Zinc 
*y 
152-5 
56-0 
Alum 
yy 
159-5 
63-0 
Sulphate of Iron 
yy 
105-0 
8-5 
Pale green. 
Sulphate of Manganese 
yy 
144-5 
48-0 
Faint pink. 
Sulphate of Copper 
yy 
112-5 
16-0 
Full blue. 
Sulphite of Soda 
yy 
127-5 
31-0 
Hyposulphite of Soda 
yy 
108-3 
12-0 
Fluor-spar 
0-17 
170-5 
74-0 
Fluoride of Sodium 
Sat. soln. 0-75 in. 
159-5 
63-0 
Fluoride of Ammonium 
yy 
166-5 
70-0 
Hydrochloric Acid, sp. gr. !•! 
0-75 in. 
152-5 
56-0 
Eock-salt (solid) 
0 75 
159-3 
63-0 
Chloride of Potassium 
Sat. soln. 0-75 in. 
159-5 
63-0 
Chloride of Ammonium 
yy 
155-0 
58-5 
Chloride of Barium 
yy 
153-0 
56-5 
Chloride of Strontium 
yy 
152-0 
55-5 
Chloride of Calcium 
yy 
147-0 
50-5 
Chloride of Zinc 
yy 
145-5 
49-0 
Chloride of Manganese 
104-5 
8-0 
Faint rose-colour. 
Chloride of Tin (SnCl) 
yy 
108-5 
12-0 
Spectrum cut off abruptly. 
Chloride of Tin (SnCl,) 
Strong solution. 
114-5 
18-0 
Spectrum cut off abruptly. 
* I am indebted to my friend Professor W. H. Milleb, of Cambridge, for the opportunity of examining 
the diamonds and sapphires alluded to above. I was a slice of diamoud bounded by cleavage-planes, from the 
Warburton Collection, m a somewhat thicker slice from the same collection. A a large octahedral diamond 
from the Humian Collection ; all these were colourless. The sapphire 24 was a large six-sided prism from 
the Brooke Collection ; that marked B was a smaller prism of a faint bluish tinge from Professor Milleb’s 
own collection. « is a colourless crystal of sapphire from the "Warburton Collection. I made an application 
to the Trustees of the British Museum for permission to use some of the limpid specimens in their collection, 
but was informed that even for such a purpose the Act of Parliament forbids them to allow any mineral to 
pass off their premises. Mr. Maskelyne was kind enough to lend me a fine colourless topaz from his own 
oUection. — [Feb. 1863.] 
