And the ice itself may be employed to concentrate them. With an ice-lens in the polar regions Dr. Scoresby has often concentrated the sun's rays so as to make them burn wood, fire gunpowder, and melt lead; thus proving that the heating power is retained by the rays, even after they have passed through so cold a substance. By rendering the rays of the electric lamp parallel, and then sending them through a lens of ice, we obtain all the effects which Dr. Scoresby obtained with the rays of the sun. [Illustration] THE ORGANIC WORLD (FROM THE ELEMENTS OF SCIENCE.) BY ST. GEORGE MIVART F.R.S. The number of all the various kinds of living creatures is so enormous that it would be impossible to study them profitably, were they not classified in an orderly manner. Therefore the whole mass has been divided, in the first place, into two supreme groups, fancifully termed kingdoms--the "animal kingdom" and the "vegetal kingdom." Each of these is subdivided into an orderly series of subordinate groups, successively contained one within the other, and named sub-kingdoms, classes, orders, families, genera and species. The lowest group but one is the "genus," which contains one or more different kinds termed "species," as e.g., the species "wood anemone" and the species "blue titmouse." The lowest group of all--a species--may be said to consist of individuals which differ from each other only by trifling characters, such as characters due to difference of sex, while their peculiar organization is faithfully reproduced by generation as a whole, though small individual differences exist in all cases. The vegetal, or vegetable, kingdom, consists of the great mass of flowering plants, many of which, however, have such inconspicuous flowers that they are mistakenly regarded as flowerless, as is often the case with the grasses, the pines, and the yews. Another mass, or sub-kingdom, of plants consists of the really flowerless plants, such as the ferns, horsetails (Fig. 1), lycopods, and mosses. Sea and fresh-water weeds (_algæ_), and mushrooms, or "moulds," of all kinds (_fungi_), amongst which are the now famous "bacteria," constitute a third and lowest set of plants. [Illustration: FIG. 1. HORSE-TAIL (_Equisetum drummondii_).]