390 Scientific Intelligence. [Nov. 
in a great number of limestones; but it also exists in other associations. 
At Baldissero and at Castella-Monte, it is mixed with silicate of mags! 
nesia and with quartz; and in the Isle of Elba, it is mixed with pure 
silica, which is in a particular state. Four varieties of this carbonate 
were subjected to an analytical process similar to that described in the’ 
foregoing article ; the results were as follows: 
Baldissero. Castella-Monte, Coe Elba, No. 2. 
Magnesia. .... w/o 1OF4O, boo 68 O'ZBS 0). was. OB GD) wtaisin ulti hi 280 
Carbonic acid... O'4]8 ...... OOS pd x: B5. OB Ai sisis aes 0:360 
Silica)! ... sisies sidiac: O:094 crsyereleer OPA BB rd srcieie 0°266 ...... 0°206 
Waterss cic ticc: O'048, . cco, OF120 6 oars O'010 wo oicis 6 0-045, 
Lime ...... cletelo re’ S=Sh. ecto steve Wm wees me we weeny O1140 
Qeantarat: welt eisic road eceeoe 0:085 eevee are eevee — 
| 1-000 1-000 1-000 0-981 
Or 
Carbonate of mag. 0°810 ..... 2 OZUS ses. ONAN rents 0'480 
Carbonate of lime. — ...,.. — .w.secee SS oe 0:250 
Sittca. 2... ee, OGIO ONS a) UL Ie O6s ie . 0-206 
TRB OTCHIA ee eo UDO ee sens, GOT yee re ee ee 
The quantity of water was obtained by distilling it from the mineral 
in a retort into a small glass tube ; that of carbonic acid by calcination, 
the weight of the water being subtracted from the loss. 
In the mineral of Baldissero, the magnesia which is not combined 
with carbonic acid, bears the same proportion to the silica as it does in 
magnesite. In that of Castella-Monte, the proportion of the latter is 
much greater ; and in those of Elba, the magnesia is entirely saturated, 
leaving the silica free: this silica, however, like that in the calcareous 
deposits of certain mineral waters, is as readily soluble in alkaline solu- 
tions as if it had been obtained in the decomposition of a silicate by an 
acid. 
When the carbonate of Campo is treated with a strong acid in a boil- 
ing state, the magnesia is gradually dissolved with effervescence; but 
the fragment neither changes its form, nor wholly loses its cohesion ; 
when the solution is poured off, it is found to be semi-transparent like 
hydrophane, but by desiccation it becomes opaque, and of a very beau- 
tiful white. It dissolves without residue in boiling liquid potash, and’ 
the solution gelatinizes with acids. : 
‘Tt results from these experiments, that it is not always possible to 
isolate by means of alkaline solutions, native uncombined silica, from 
the silica which we separate from a combination by an acid.”— (Ibid. 
p. 315.) 
IV. On the Greek Fire of the Middle Ages. By Dr. Mac Culloch. 
In No. xxvii. of the Journal of the Royal Institution, is an interesting 
memoir by Dr. Macculloch, respecting the history and nature of tliis 
celebrated subject of inquiry and discussion. The following is a con- 
densed view of the investigation. 
The subject of the Greek fire, sufficiently obscure in itself, appears: 
to have been rendered much more so, by collateral causes, and princi- 
