Each of the clips, A, secured to the axle, is provided with a swinging bolt, a, whose free end is held by a pin, h, between eyes formed on the ends of the other arm of the clip. The thill iron, C, is made with a forked eye to receive a loop, D, through which passes the swinging bolt, a. Between the sides of the Ioop and in front of the bolt is journaled a rubber roller, g, which holds the loop into close engagement with the bolt. To the floor of the wagon is secured a rest, E, for the rod, F, to the bent ends of which are secured chains connected with the pins, h. When it is desired to detach the horse—as in the case of a runaway—the rod, F, is raised, thereby drawing the pins, h, from the bolts, which turn on their pivots and release the loops, thus disengaging the thills. Therubber roller prevents rattling, and when the swinging bolt is released the rubber rolls along the bolt and facilitates the release of the loop. This invention has been patented by Messrs. C. H. Keenan and J. P. Gardner, of Fort Halleck, Nevada. Musical Fishes. Speaking of the musical perch of the Ohio River, W. H. W. says: “The humming or singing is produced by two corrugated bones in the mouth or throat, which they rub together, and the sound is on the principle of the violin or musical glasses. I intend as soon as I can get a good specimen to dissect, or have it done, and hope to give you an item, as I do not thinkit; has ever been noted in any work or paper." Determination of the Calorific Power of Fuel. The process consists in burning one gramme of the coal. or fuel in a small platinum crQ.cible, supported on the bowl of a tobacco pipe and covered by au inverted glass test tube, through which ifpassed a stream of oxygen while the' whole is placed under water in a glass vessel. The oxygen is fed into the test tube by a movable copper tube, which may be pushed into the test tube so as to come immediately over the crucible. The coal burns away in a few minutes with very intense heat, and the hot gases escape through the water—the bubbles ' being broken up by passing through sheets of wire gauze, which stretch between the test tube and the walls of the vessel containing the water in which it is placed. The temperature of the water is taken before and after the experiment, and from the figures thus obtained the heating power of the coal is calculated. THE Agricultural Department at Washington has just sent out large quantities of the eggljo'Of the silk worm by mail to all parts of the country. It has now been satisfactorily demonstrated that the leaf of the Osage orange makes as good silk as that of the mulberry, and that the worms will feed upon it and thrive. The Department is in receipt of letters from girls in various parts of the country, saying that they' have made from $20 to $100 by raising silk in thilS way. 388 f JUNE 19, 1886. Cast Iron Beam*. Absolute strength in the iron of large castings is of little consequence unless they cool, after pouring, in such a manner as not to leave them subject to consider able internal strains. We know that the late Professor Hodgkinson found that with the iron he experimented upon the compressive strength was six times that in tension, and hence that the bottom flange of a cast iron girder should have six times the sectional area of the top flange. But very few, if any, engineers adopt such a proportion, as the casting would, in all probability, crack in cooling. Most of my audience have seen the cast iron bridge over which the London and Northwestern Railway crosses the Regent's Canal. The first girders for this bridge were cast at the Tinsley Park Works. The iron made there was very hard ; and I have been told by my friend, Mr. Shanks, who was engaged there at the time, that it would chill to a depth of two inches. It was used, among other things, for making rollers to roll steel. The Regent's Canal bridge [drawing was sent down there, and they made the patterns and cast the girders. They broke through and through in cooling. Then they altered the patterns, and by pulling ' off the sand from the thicker portions of the castings, so as to equalize the cooling, a number were cast with the loss of one out of every six.. At last, six were sent up to London, and of these every one broke in a thunderstorm. Other girders were then cast of different form. Castings, overstrained in cooling, are apt to break under even a moderate degree of vibration ; and the late Mr. Rastrick, once of the Bridgenorth Foundry, and afterward Engineer-in-Chief of the London and Brighton Railway, once stated in evidence how a number of cast iron boilers he had made cracked open after a peal of thunder.—Z. Colburn.