Page:Popular Science Monthly Volume 49.djvu/883

Rh shining may be extinguished, as M. Mesnard has shown, by the introduction of a quantity of air inversely proportioned to the strength with which it is charged with turpentine. Spirit of turpentine may thus be made a common standard for the different essences, and we may regard as the measure of the intensity t)f the perfume disengaged by a given weight of an essential oil the ratio between the weight of the turpentine which will neutralize the perfume and the weight of the same substance which under corresponding conditions will act upon phosphorescence with corresponding energy. M. Mesnard has devised an ingenious apparatus for performing practical measurements by the application of this principle.

Cordite.—According to the Industrial World, the manufacture of cordite is very simple. Nitroglycerin and dried gun cotton are mixed together in accurately weighed portions, the liquid nitroglycerin being poured over the gun cotton and mixed by hand until it is all taken up by the cotton, producing a dirty-white mass which looks much like sugar. This mass is then placed in kneading machines, which mix in the proper proportion of acetone. After several hours' kneading some vaseline is added and mixed in by further kneading. The mass finally becomes a stiff dough, which can be readily molded into any desired shape. The combination of nitroglycerin and gun cotton with acetone produces a compound quite different in appearance and properties from either of its components. Cordite is a heavy substance which burns only on the surface, the violence of whose explosion can hence be readily regulated by varying the relation between surface area and volume. Both nitroglycerin and gun cotton are very unstable. Cordite, on the other hand, is quite the reverse. Thus, a bonfire made around eight cases piled up against each other simply burned up the boxes and then the cordite, no explosion occurring.

Death of Prof. Ernst Curtius.—Dr. Ernst Curtius, Professor of History and the Fine Arts in the University of Berlin, who died July 12th, aged eighty-one years, was one of the most distinguished and most learned historians and archæologists of the century. He was born at Lübeck in 1814, of a family distinguished by love for literature and art; studied at Bonn, Göttingen, and Berlin; went with Prof. Brandeis in 1837 to Greece on an errand for the furtherance of archaeological research; afterward, with Ottfried Müller, spent four years in Greece in historical and archaeological studies, and began in 1864, but carried on with great activity after 1875, the excavations at Olympia which have been rewarded with the richest and most abundant treasures of classic art. From 1844 to 1849 he was extraordinary professor at the University of Berlin and tutor to the crown prince. In 1856 he was elected professor at Göttingen, but returned to Berlin as professor in 1868. His History of Greece is rivaled in merit only by Grote's, and is its fitting complement, supplying what Grote's lacks as Grote's supplies what it lacks, and is distinguished by the life it gives to the old legends and its appreciation of the artistic genius of the Greeks. He also published—works of equal merit in their respective fields—a book on the Acropolis of Athens (1844) and an account of the Discovery of Olympia (1882), besides many smaller works and monographs.

Plant Breeding.—In a recent copy of Nature M. T. Masters has an interesting article on Plant Breeding, from which the following extracts are taken: The natural processes of variation in the plant world as controlled by the art of the gardener are well typified in the garden rose of to-day—quite a different flower from those roses of our forefathers, which have, with a few exceptions, totally disappeared. It is the same with peas and potatoes and with most other plants that are grown on a large scale. The two methods made use of by gardeners for the improvement of plants are selection and cross-breeding, the latter, as far as results are concerned, only a modification of selection. The natural capacity for variation of the plant furnishes the basis on which the breeder has to work, and this capacity varies greatly in degree in different plants, so that some are much more amenable and pliant than others. The trial grounds of our great seedsmen furnish object lessons of this kind on a vast scale. The two processes are antagonistic. On the one hand, every care is