3. The Breath-cohesion Figures of Sfrethill figures were discovered by Dr. Strethill Wright of Edinburgh, and communicated to the royal Scottish society of arts on Dec.12. 1864. This author, who had long been engaged in observing phenomena connected with the modification of cohesive attraction produced between solids and fluids by heat and electricity, was induced to take up the subject afresh by the publica tions of Tomlinson, and one of the results was the production of his so-called "breath cohesion figures." He employed as the recipient surface a freshly-split. and therefore chemically clean, surface of mica; on this lie placed a single drop of the fluid to be experimented on. He then breathed upon the surface, and instantly the drop flashed out into a figure characteristic of the fluid of which it was composed. By this means, a variety of substances, such as vegetable extracts, tinctures, and essential oils, and ani mal fluids, such as serum, vaccine lymph, bile, mucus, and urine in its various patho logical conditions, could be examined. By dusting the figures with hair-powder or lycopodium, he was also enabled to render them permanent, and to exhibit them in his lectures, expanded to a diameter of 14 ft. by the oxyhydrogen microscope. In general appearance, the breath-cohesion figures bear a strong resemblance to vegetable forms, especially to the fronds of the desmidiece. In many Of them, as in the desmidiece, a very distinct bilateral symmetry is apparent. Others, again, simulate the forms of the larger alga. A great many are resplendent with the hues of the soap-bubble, arranged in concentric bands and curves of excessive beauty; while others are veined throughout so as to resemble sections of agate. Dr.Wright considers that the breath-cohesion figure
is the product of electric attractive force developed on the freshly-split mica, as a well known consequence of cleavage.
4. The Electric-cohesion Figures of Strethill Wright.—These figures were described by Dr. Wright to the royal Scottish society of arts on April 11, 1864, and are produced by electrifying drops of various fluids placed on a clean plate of glass, vulcanite, mica, or other smooth non-conducting substance. By this method, an endless variety of beauti ful dendritic figures are produced, differing not only with the fluid employed, but also with the slightest change in the character of the surface on which it is placed, and with the electricity, whether positive or negative, which is imparted to the drop. The elee tric-cohesion figures are produced in the following manner: A sheet of plate-glass is laid upon a plate of blackened metal, and in the center of the glass a drop of the fluid to be operated on is deposited with a clean glass rod. The metal plate and the drop are then connected with the opposite poles of an induction coil (capable of giving a spark of about half an inch in length) in full action, and immediately branches protrude from the drop, which slowly creep over the glass until they closely cover a circle of 4 or 5 inches. Sulphuric acid, and solutions of potash, deliquescent salts, and organic fluids, give the best figures; while nitric and muriatic acids and distilled water do not form figures under the electric influence.