JSCIExNimO SUMMARY, 
101 
because it forms the first instance of the occurrence of this metal in nature 
in combination with the hyaloid elements : chlorine, bromine, and iodine. 
The^composition of iodobromite, as he has termed it, is : 
Found. 
Calculated. 
Silver 
59*96 
60-88 
Iodine 
15-05 
14-15 
Bromine . 
17-30 
17-18 
Chlorine . 
7-09 
7-79 
99-40 
100-03 
In the third column of the above table are given the percentage numbers 
corresponding with the formula 2Ag (01 Br ) + Ag I, which appears to be 
that of the new mineral. Iodobromite occurs in small regular octahedra of 
a yellow colour, some of them inclining more to the greenish hue of olivine. 
The crystals have a close resemblance to those of the bromyrite of San 
Onofre, near Zacatecas, Chanarcilla, and Hiielgot ; they are malleable and 
sectile. None of the specimens of embolite (silver chloro-bromide) hitherto 
examined contain iodine. The iodides of sodium, zinc, &c., crystallise in 
forms belonging to the cubic system, and the fact of their being isomorphous 
with the corresponding chlorides and bromides of these metals points to 
the probability of the existence in nature of a silver iodide crystallised 
in the regular system. The silver iodide, as yet met with, has 
been found in hexagonal crystals closely according in their forms with 
crystals of greenockite. 0. Lehmann has recently prepared ( Zeitschrift fur 
Kry stall. 1877. I 492) the iodide artificially in crystals which are 
regular. Von Lasaulx’s discovery is of interest in its bearing on the isodi- 
morphism of this group of salts. — Jahrbuch fur Minerologie , 1878, 649. 
Occurrence of Liquid Carbonic Acid in Syenite . — In his u Geological Report 
of New Hampshire ” Howes describes the occurrence of liquid carbonic acid in 
the microscopic cavities existing in sections of the New Hampshire rocks. 
Although the number of sections examined was not large, the cavities were 
never met with in any of the granitic rocks except in a syenite from Colum- 
bia, and here they were found in the greatest abundance, and under circum- 
stances which render their occurrence remarkable. The syenite referred to 
is white, spotted with black ; macroscopically orthoclase and hornblende 
alone were recognisable. In thin sections, however, plagioclase, biotite, 
quartz, and apatite were seen, and, moreover, calcite, a mineral rarely 
occurring in granitic rocks. The quartz is present in small amount only, 
occupying angular interstices between the other ingredients ; but’each grain 
is filled with cavities which are quite large, and many of these contain liquid 
carbonic acid. Its presence in connection with calcite may indicate that 
calcium carbonate was a constituent of the sedimentary material of which 
this rock was formed, and that at the temperature at which crystallisation 
took place a reaction between the silicic acid and the carbonate resulted in 
the liberation of carbonic acid. — Amer. Journ. Sc. 1878, xvi. 326. 
