Of the geological age of the building stones used in the United States, George P. Merrill observes, in his report to the Maryland Geological Survey, that few stones are used to any extent that are of later date than the Triassic, and few, if any, of our marbles are younger than the Silurian, while nearly all our granites, as now quarried, belong at least to Palæozoic or Archæan times. Stones of later age than Triassic are, so far as relates to the eastern United States, so friable or so poor in color as to have little value. GENUINE STARCH FACTORIES. BY BYRON D. HALSTED, SC. D., RUTGERS COLLEGE. Much in this world is neither upon first nor last analysis true to name. From the corner grocery we buy a pound of starch in a rectangular package highly decorated with lithograph and lettering, setting forth the excellences of the product, “superior to all others,” and manufactured, with the utmost care, by Messrs. So-and-So. The fact is that the big seven-story establishment did not make a grain of the starch, and the best that can be claimed is a satisfactory method of bringing the product already formed into the present acceptable condition. But it is not the purpose of this paper to decry the refineries, whether they be of starch, sugar, or this or that of a hundred natural products, but to direct attention to the source of that very common and, it may be safely said, indispensable substance known to the English-speaking people as starch. [Illustration: FIG. 1.--STARCH GRANULES OF THE POTATO.] It will be no new surprise to state, by way of introduction to the subject, that starch is the ordinary everyday product of ordinary everyday plants. So humble a vegetable as the potato has gained its way into all lands of the more civilized peoples almost solely because it has a habit of storing away, in large underground stems, a vast amount of starch. Let this provident tendency disappear in this plant for a single season, and the crop growers would discard it from their list of remunerative plants, while millions of people would turn with dismay to some other source of a daily supply of starch. What this change in the nature of a single kind of plant would mean to the human race words can not describe. If the famine in Ireland of 1845 and some later years, induced by a rot in the potato, is any index, the misery would be something worse than we should care to even dream of. When there is a shortage of starch in India, a distress follows that is felt through the bonds of sympathy, if in no other way, the whole world round. Let rice fail to mature its grain, which means, in short, not to store its starch in available form for man, and the dependent race is brought to the ghostly condition of starvation and thrown upon the charity of those people whose starch is in their grain elevators, sacks, and barrels almost without number. [Illustration: FIG. 2.--STARCH GRANULES OF CORN.]