Besides the difference of sensitiveness toward the solar spectrum, these modifications of silver bromide exhibit other characteristic differences in properties which indicate beyond a doubt that they are two essentially different modifications of the same substance. Among these are, 1st. Their unequal divisibility in gelatin or collodion solutions. The indigo sensitive silver bromide cannot be distributed through a gelatin solution, while the blue sensitive modification does so very readily. 2d. Their unequal reducibility; the blue sensitive silver bromide being reduced with much greater difficulty than the indigo sensitive variety. 3d. Their different action toward chemical and physical sensitizers. 4th. Their different action toward photographic developers. 5th. Their different action under the influence of heat. The blue sensitive variety if heated under water has its sensitiveness perceptibly increased, while the other is not changed by such treatment. A direct transformation of one modification into the other has not yet been accomplished. The effect of the light upon these substances is incipient reduction, and we might hence suppose that the more reducible indigo sensitive variety would be the more sensitive to light. But this is not the case, because it is not chemical reducibility, but the absorption power for light that is of the greatest importance. Now the blue sensitive silver bromide has a greater absorption power than the indigo sensitive variety, and hence its greater sensitiveness. Silver chloride prepared by methods similar to those used in making the two forms of bromides was also found to exist in two modifications. One is designated as ultra violet sensitive, the other as violet sensitive silver chloride.--_Amer. Chem. Jour_. * * * * * ANALYSIS OF A SAMPLE OF NEW ZEALAND COAL. [Footnote: Read before the Society of Public Analysts on the 28th June, 1883.] By OTTO HEHNER Some discussion having recently taken place as to the value of New Zealand coal as a fuel, the following results of a somewhat full analysis may be worthy of being placed on record. The sample to which the results refer consisted of large brownish black lumps, many of which showed woody structure; the fractures were conchyloid, the surface shiny and highly reflecting. It was interspersed with a considerable amount of an amber colored resin. When powdered it appeared chocolate brown. It burned readily, the flame being bright and very smoky. Its ash was light and reddish brown. It consisted of-- Water (loss at 212° F.) 20.09 Organic and volatile matter 75.19 Ash 4.72 ------ 100.00 The organic and volatile constituents had the following percentage composition--