Page:Popular Science Monthly Volume 45.djvu/591

Rh traverses an atmosphere containing a very moderate quantity of dry coal dust, the dusty atmosphere will explode with great violence, and the explosion will continue and pass throughout any length of such atmosphere, its violence and force increasing as it progresses. The coal dust from several seams in certain different districts is almost as sensitive to explosion as gunpowder itself, the degree of sensitiveness increasing in proportion to its high quality and freedom from impurities. In mines which are briskly ventilated there is a greater probability of explosion, while in such cases it is generally more severe. One of the most important results of the experiments made has been to demonstrate that certain high "explosives" (roburite, ammonite, etc.) are incapable of igniting or exploding coal dust. Mr. Hall, in face of these facts, is therefore led to urge the total abolition of gunpowder from coal mines for blasting purposes and the substitution of certain "high explosives"—precautionary measures which many large firms have already adopted. Apart from the danger of using gunpowder arising from the ease with which it starts a dust explosion, it appears that in mere handling alone four hundred lives have been sacrificed during the last twenty years, while the loss of life from explosions caused by gunpowder during the same time has been at least one half of the total loss—viz., 4,098 persons. With regard to preventive measures, every possible effort, it is recommended, should be made, either by watering the dry dust or removing it to avoid accumulation, so that any accidental ignition of fire damp may be limited in its effects and prevented from developing into a sweeping explosion through the agency of dust.

Birds of Michigan.—The Bird Fauna of Michigan, as described by Mr. A. J. Cook in a bulletin of the State Agricultural Experiment Station, being protected by the Great Lakes nearly surrounding the State, is very interesting. As is shown by Dr. C. Hart Merriam's colored map, it embraces representatives of three distinct faunas—viz., the boreal in the north, which includes the northern peninsula and the northern part of the southern peninsula; the transition, which occupies nearly all the southern peninsula, and reaches slightly into Indiana and Ohio; and the upper Sonoran, which, though mostly to the south of Michigan, reaches into the southeastern and southwestern corners of the State. There are met in Michigan many birds peculiar to the far north, and others that dwell for the most part in the States and countries to the south, even reaching to and beyond the Gulf. The first are illustrated in the Bohemian waxwing, the spruce partridge, the Canada jay, and the pine grosbeak; and the summer redbird, the mocking bird, and the cardinal redbird illustrate the second group. The large lakes attract many birds that are usually maritime, like the gulls and the terns; while in southern Michigan, with its prairies and woodlands, both widely distributed, are found the prairie fauna, as illustrated in the pinnated grouse, and those birds which are most at home in the forests of wooded areas, like most of the thrushes and the warblers.

The Future Work of the American University.—Addressing the Pennsylvania State Board of Agriculture on the Progress and Practical Value of Agricultural Science, Dr. Peter Collier gave a prominent place in illustration to the work that has been done in the analysis of fertilizers, whereby frauds have been exposed, and farmers have been pecuniarily benefited by the cheapening of fertilizing materials and the assurance of increased and improved crops. A further illustration is found in the progress and practical applications of bacteriology a word which, together with bacteria, does not occur in the standard dictionaries of 1868 by means of which the causes and cures of the most serious maladies that affect crops have been discovered and brought within the reach of all, and such operations as the making of butter and cheese are facilitated. One would not have imagined a short time ago that physics and physiology were the sisters of psychology, or that ethics should consort with economics and sociology in the same laboratory, or that a professor of institutional history should commend to his pupils biology as a minor subject. Yet all these things have really happened. Indeed, only since Darwin and Spencer has it been possible to discover the essential kinship of the various branches of knowledge. Projecting