The communication entitled ., A Belt Problem" calls to mind a discussion in the Mechanical News a few years ago in regard to the same subject, and in wbich the first writer observed the same phenomenon that Quirk mentions. The ., crawl" of the outer belt is explained by the fact that it runs OIl a pulley larger, by twice the thick ness of the belt, than that on which the inner one runs, and, provided there were no loss, it would gain the thickness of the inner belt, say x X 2 X 3'1415 + at each
... X 3'1415 + at each revolution. It is readily seen from this that if the pulleys are of different sizes, and make a different number of revolutions, the outside belt will gain more rapidly on the smaller pulley, thus causing unequal tension. In case tlte small pulley is the driver, the outside belt will be tightebt on the working side, which, pro' vided the difference were not too great, is as it should be; but if the driver is the larger, then the outer belt would bel slack on the working side and have a ten dency to hold back; which would go far to overcome the advantage gained by the extra grip given by the extra weight, and would certainly add much to the strain on the inner belt, which would not only have to do all the work, but overcome the" crawl." 'l'he use of a double bel t becomes then a useful makeshift in some cases, where the driver is slightly smaller or of the same size as the driven; but in other cases there is probably more loss than gain, and even under favorable circumstances it is of questionable utility for continued use, as the slip of one belt upon the other would probably cause a great amount of wear; and the two beits run side by side, or a single belt of twice the width, would be much more durable and give more power. W. D. G. Cloquet, Minn., October 13, 1890. �titutifi' �lUtti,au. The San Jacinto '.I'ln Mine.. I more extensive ones on the Cajalco lode, the develop-A recent number of The Engineering and Mining I ments consist of a number of "test pits" sunk to vari Journal contains a description of the tin deposits of ous depths-usually from 2 to 12 feet-in the croppings San Jacinto, San Bernardino County, California. In, of different veins, all of which show more or less of the of cardboard, and, should the price of gas vary, the From the most westerly to the most easterly vein the have not yet been discovered, is, from the point of thfl dial will have to be removed and replaced by one Show-I distance is, as the crow flies, about three and a half nostril to the root of the tail, about twenty-two feflt. ing the altered price. I! is conceived that this arrangemiles, and within this space upward of 70 lines of crop-This is greater than that of the celebrated Mastodon ment will lead to the use of gas by many small conpings of apparently as many different veins were found. giganteu s discovered near Newburg, N, Y., in the sumers who distrust gas meters because they cannot They were practically identical in character; a sort of summer of 1845, and the skeleton, as a whole. is larger understand them, and who doubt the correctness Qf syenitic rock which, in Cornwall, is known as •. tin and more complete than any that have been founlt in gas bills because they cannot check tbem. cape�" 9f 'I Jode granite." Witb the exceptioll of the Kentucky, Ohio, Missouri, California, or Oregon, The Bo"ot!llov Volcano. The most interestin g result of the recent trip of the Rush was a visit paid by the officers to Bogoslov Island, where is the famous volcano of that name. In conversatioa with one of the officers, an interesting Tesume was obtained of the discoveries and data gleaned by the visit. Bogoslov is sixty miles west Bouth west of Oonalaska. It originally consisted of one island with two craters, one of which first sprang into activity in 1792. Last winter the island was the scene of a strange convulsion of nature. The second crater, now known as New Bosgoslov, became active. In some powerful convulsion the sands pit which had connected the two parts of the island was subme rged, and one crater was separated from the other by several fathoms of water. It is thought that during this convulsion changes occurred in New Bogoslov below the water line; that fissures were opened, through which volumes of water made their way into the caldron within. This accounts for the immense quantities of steam which the officers of the Rush saw escaping from the crater at a distance of fully sixty miles. Of the two craters, New Bogoslov offered the most interesting field of study to the officers of the Rush. They ascertained the crater to be only 200 feet above the sea level. The peak had disappeared in the gaping hole. Along the sides of the volcano large deposits of lava, pumice, ashes, and volcano rock were seen. From fissures on the level earth springs of boiling sulphur arose to heights of from seven to ten feet. The officers planned an ascent to the crater-a hazardous feat which could only be attempted when a favorable wiud carried the sifting volumes of sulphurous steam in a single direction. When near the mouth of the crater the footfalls of the officers were echoed within the vol cano. On peeping over the edge of the mouth an impressive sight was witnessed. Stea.m in endless quantities rushed up from unknown depths, and rum bling, bubbling noises, like that of th under, were heard. The air was impregnated with sulphur, and near the crater one could breathe only with difficulty.