The marriage of fire and water has given birth, in these latter days, to a power immensely stronger than either, and yet more easily controlled. But, if through ignorance of its nature or carelessness of its requirements, this power is permitted to assume the leadership, its anger recognizes no curb and its strength no opposition. As a master, steam is merciless ; as a servant, docile. To restrain and guide this power, under all circumstances, is the object of the nightly dreams and daily efforts of engineers, the world over, and steam boiler explosions are to be prevented, or their results shorn of their harmfulness to life and property before this power can be said to be fully under control. Therefore, the proper construction of steam boilers is a subject of personal interest to every one whose life or property may be affected by the consequences of an explosion, and in one or the other of these classes may be reckoned almost every member of a civilized community. The chief points to be considered in a perfect boiler are safety, economy, durability, and ease of management and facility of control. Sectional boilers have for a number of years been growing gradually into favor because of their more nearly fulfilling these conditions than those of other types. They are portable, easily handled, readily removed, set up, repaired, and enlarged, are rapid generators of steam, free from danger of disastrous explosion, easily kept in order, simple in principle, and direct in operation. Mr. John B. Root, of New York city, well known as a successful in-#vehtor and as a builder of engines and boilers, is now constructing boilers of the pattern shown in the accompanying engravings, more than one hundred of the boilers being now in use. As seen from the large (perspective) engraving, the boiler is a collection of parallel tubes of wrought iron, set on an incline of about two inches to the foot, from the front, back. The same letters refer to the same parts in each engraving. A represents the tubes, B, the heads of cast iron, square in their superficies, and into which the tubes are seated by means of screw threads on the ends of the pipes and in the heads. C is the front plate on which the lower section of heads rests, and which also supports the superincumbent weight of that end of the tubes. D is the connecting elbows forming passages between the pipes, being held in place by the nuts, E, over saddles that have a bearing on the corners of three elbows. In the Heads, B, are recesses in which are placed glands of rubber forming elastic joints to allow for expansion and contraction. F is the injection pipe for the feed water, situated at the rear of the boiler, and leading to the lower end of the lower tier of tubes. Q is the steam connection of the upper tier of tubes on which is seated the safety valve, H, and from which the steam is led to the engine. K i3 the grate, L the front of brick work, M the floor of the ash pit, N the steam-gage pipe, O the inclined bridge wall at the back of the furnace, Q (dotted lines) is the stack for escape of the smoke, _____ t, bolts connecting the side framing for the t?rick work, and X a steam dome, if required, on which, if used, the safety valve, h, and steam eduction pipe are placed. A damper, V, is placed in the flue at the rear when desired. The larger engraving represents only a portion of the boiler, some of the sections being removed. The tubes are placed zigzag, not directly-t)ver one another, which arrangement brings their surfaces nearer together, while, at the same time, it allows space between them for cleaning when the outsides become foul, a contingency, however, which is not expected, as the arrangements of the furnace arc intended to insure almost perfect combustion. The inclination of the tubes and their connection with each other by th e plates or caps, D, are designed to insure continual circulation of the water a very important point and the heated gases of combustion, being compelled, by the arrangement of the tubes, to impinge upon or envelope all portions of their outer surfaces, are fully utilized before being discharged into the stack. The circulation of the water in the tubes keeps them free from scale, but if deemed necessary to examine them it is only required to remove the elbows, D, for the purpose, A boiler may be enlarged by adding tubes at the top and side of the boiler, as all the connecting parts are in sections. The inventor sets forth the advantages of his boiler l?y the following claims: First, safety; owing to the small diameter of the tubes, not over five inches, and tested to 500 lbs. to the square inch. In case of burning or cracking, no explosion can occur, but only a rupture, confined in its effects solely to the tube affected. No case of rupture has yet occurred during the two years these boilers have been in use. Second, economy ; the inside surfaces constantly washed by rapid cir culation, and the products of combustion flame, heated gases, smoke thrown against every portion of the heating surfaces by eddies which change the otherwise diretc course of the draft. Third, durability; preventing bad results of unequal expansion and contraction by the use of elastic joints* impossible in shell boilers, which, owing to greater necessary thickness and variation of the amount of that thickness, as where joints occur, en* courage unequal expansion, and suffer most from varying temperatures. Finally, cheap and quick removal of an injured part (no weakening by patching), and facility for examination and cleaning of either inside or outside surfaces, and, also, facility of enlargement without" disturbing the boiler as first erected. Mr. Root is now putting in a 200-H. P. boiler of this pattern for one of the oldest and largest iron manufacturing concerns in Philadelphia. All communications should be addressed to John B. Hoot, 95 and 97 Liberty street, New York city. Many a city and town, says the Boston Journal of Chemistry, has had to deplore the loss of fine shade trees, by carbureted hydrogen gas coming in contact with their roots, and poisoning them by being absorbed. There is a strange instinct in the roots of plants or trees. As if they had eyes to see, they bend and stretch in the direction from which they can derive nutriment; and wherever they can have free and easy access to the soil and find food, there the number and thickness of the filaments are augmented. If we plant a tree in hard, unyielding soil, it will struggle most wonderfully to sustain it-self, by pushing its roots through the packed earth. If, under these circumstances, a trench is dug ten, or even twenty feet from the tree, filling back the loosened earth again into it, the roots appear to be cognizant of the fact, and commence a struggle with the impacted soil, to reach the- trench ; and this fact explains how it is that the roots of trees* are destroyed by gas. The trees upon the sides of streets are placed 3j hard soil; an$i when the trench, is dug for the ga# pipes, and the earth returned, the roots instinctively push for the trench as a point of relief, or where food can be more easily secured. We have seen gas pipes, after having lain for several years, perfectly covered with a network of roots proceeding from the neighboring trees. Now, if there is the slightest leak in the line of pipe, the gas moves in the direction of least resistance, and that is along the trench in which is placed the pipe ; hence, the tender spongioles are presented with strange and poisonous food, the gas is absorbed, and the tree dies. We can hardly suggest a remedy for this great evil. It may be well to compel gas companies to cover their pipes, in the vicinity of trees, with a thick coating of cement, or plank the walls of the trench, so as to prevent the tree roots from passing through. The loss of fine shade trees in cities and towns is almost irreparable, and every practical method should be adopted to prevent it.