expression and especially against misstatements such as: "The following AgC1." What the reaction took place: NaCl f AgN03 --t NaNOa writer of such a statement means and should, therefore, write, is: 'The reaction represented by the following equation took place: NaCl AgNOs --t NaN03 AgCl." Realizing the fact that habits, once formed, are usually permanent; that imperfect and hazy expression is a scientific fault to be overcome with other scientific faults; that the mastery of English is a mark of education; and that we, as scientific teachers, have an especially good opportunity to foster clear thinking in our students by insisting on clear expression of ideas, let us not continue to neglect one of our great opportunities of service.
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Gelatin Aids Digestion of Milk and Ice Cream. Gelatin is a protein, hut it never would be a v w successful meat substitute. Its best use is as an aid t o the digestion of . milk when other foods are excluded from the diet, Dr. Thomas B. Downey of the Mellon Research Institute has found. Barley water, which is a member of the same class of protective colloids, has long been a common and useful component of the contents of many a baby's bottle. "Gelatin," says Dr. Downey, "was introduced as an economy food during the period of the French Revolution. I n view of the status of the knowledge of nutrition of that day, i t is not surprising that there arose exaggerated opinions, both pro and con, regarding the actual food value of the product. It is only in quite recent times that the results of earlier investigations on gelatin as a foe$ can be interpreted with accuracy." I n his experiments with rats Dr. Downey found that i t was of decided supplementary use with such natural foods as wheat, oats, and harlel'but had little value as a major source of protein. Rats fed on milk and the average commercial variety of ice cream oicked uo considerably in growth and health, however, when gelatin was added t o the i ~ t effects of gelatin as a colfoid of the emulsoid type bill of fare. He c a n ~ l u d e s ~ t h"the exert a significant influence upon digestibility and absorption where ingested with these dairy products with the exclusion of other foods. I n these particular diets, the colloidal effects of gelatin may he equal in importance to, if not indeed greater than, its value as a protein."-Science Senice Star Measuring Device Applied to Microscope. The interferometer, invented by Dr. A. A. Michelson, of the University of Chicago, and used a t the Mt. Wilson Observatory t o measure the diameters of distant stars, has recently been applied in Germany t o the microscope for measuring particles too small t o be seen with the ordinary microscope. The method depends a n the fact that when the light from a very minute source, either because of its actual small size, or, as in the case of the stars, because of its great distance, is split into two beams, and recombined, a series of light and dark "interference" bands results. By the measurement of these bauds, the diameter of the source of light may he computed. Prof. Michelsau suggested that the method could also he applied t o the microscope, hut, so far as is known, the work of the German scientist, U. Gerhardt, is the first time that the suggestion has been carried out. It is stated that by means of the microscope interferometer, objects half as small as can be seen ordinarily may be measured. The smallest particle actually measured was about 1/125,000 of an inch in diameter, while theoretically, one-half this size could be measured.-Science Service
