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Kugineering. STEAM BOILER EXFLOSIONS. The following article appeared in a late issue of tlie Mechanical News from a corre- spondent Who, evidently, has got tired of this momentous question, and wishes it set right. He says: It seems to ine that we have had about nonsense enough in regard to this boiler inspection business to have some one rise and explain in what good it has resulted, as it is well known that these disasters have increased, to an alarming ex- tent since the Jaw was enacted to that end, I expect tobe called a “crank” by those high officials, but I do assert without fear of successful contradiction from any scientific source that the whole thing is a humbug «from beginning to end, and these inspectors know it to be such if they know enough about the generation of steam and the use of boilers to hold any such position. In treating upon this subject we would note the difference between the bursting of a boiler, which may be done by the force of steam by tearing off an old patch, or the collapse of a flue; but an explosion that will tear a boiler to shreds and scatter the frag- ments for half a mile around, to the terror _ of a whole neighborhood, requires something | | more powerful and sudden in execution than steam. | An instance I have in mind where a mill | was running under a pressure of 80 pounds | of steam ; the front head of an 18-foot boiler ! came out, the boiler left the arch, went ! through the building and across the road | some twelve rods like an arrow, and smashed | down a house killing the inmates; and any | one that would believe that 80 pounds of steam would do this would be the man to take stock in Keely’s motor. Does any one.ask what this power is that | - acts more like lightning than like steam or j unpowder, and is so much more disastroux i= in results? It is a well known principle that-water_is_composed-_of_two. gases, each-| of which isas inflammable as powder and ‘far more sudden in expansion when ignited | 2 than. giant powder; and there are certain | conditions in steam boilers when these gases | will become separated, and one being more | volatile than the other will pass off with the steam, while the other accumulates till it takes fire, as it generally will froma red hot flue; and in that case, no matter how thick or Btrong the boiler, if it is steel and six inches ick it must go, and the thicker and strongér the boiler the more terrific the explosion and more disastrous in conse- quences, I have just been reading of an explosion that killed nine men, and it was aserted the cause was a mystery, as they had a very strong boiler (a mystery forsooth!) An en- gineer once said to me, ‘I was running my engine, and I. could not make my pump work. I knew the water was getting low. Soon I began to smell the gas. I lost no time in drawing the fire from the arch and saved my boiler.” There has of late been considerable racket in a certain town between the council and the boiler inspector; and from from what I can learn neither of them knew what they were talking about. ‘The inspec- tor knew enough to hold his office and-draw his salary, and that was satisfactory to him. To be brief, the steam users are not as safe with this inspection as they would be with- out it, The inspector louks it over, tests it to 100 peunae and says you havea good strong boiler, and the engineer thinks the inspector knows; he recklessly drives ahead, and the result is an explosion. Ihave written these lines with the hope to elicit a more thorough and scientific in- vestigation of this subject. _ In what is estimated to be the most delicate pair of acales in the world, according to the account given in the scientific papers, the beam is made of rye straw, and together with the pans, which are made of aluminium, weighs only fifteen grains. In the most delicate scale heretofore made the beam and pans weighed sixty-eight grains—the beain being made ot aluminium—and the instru- ment being capable of weighing to the one ten thousandth ofa grain. A piece of hair one inch long being Weighed with this » wonderful apparatus was found to represent an almost infinitesimal quantity of one- thousandth of a grain. A patent has been issued for a composite pulley, formed of a cast-iron hub, a web or body made of paper, pasted and pressed into a solid block of the thickness to give it the required strength, and this web surrounded by a wrought or cast rim secured to the web by means of knees or flanges riveted through the rim and paper. The claim is made that the rim, having a uniform bear- ing upon the paper body, is steadier and more even than any iron pulley yet made. By the use of hollow steel shafting, which is now generally introduced in Europe, even for such heavy work as steamship propeller shafts, the weight ts very much lessened in roportion to the decreased strength. A 10- nch shaft with a hole 4 inchesin diameter, has its weight reduced 16 per cent., with a Joss of only 2.56 per cent. of strength. A five-inch hole would make the figures 26 and 4.25, STEAM ALARM WATER GAUGE, The alarming frequency of boiler explo- sions is causing no little perplexity ia the scientific world, and all manner of devices are handed in by ingenious inventors. The simplest apparatus to give warning of an explosion that we have yet seen is repre. sented by our illustration. Nothing is clwimed for this gauge reqnir- ing a theoretical demonstration, or which will not be agwitted at once by any ordinary mechanic, Upon the most casual examina- tion. It has now been before the publica sufficient length of time to enable it to be thoroughly tested under every possible va- riety of, circumstances, and in no instance has it ever failed to fulfill all that has been claimed for it. This invention is, as its name implies, a water gauge—an indicator of water in the steam boiler, and an instantaneous alarm for low water or approaching danger, all combined in one exceedingly simple appa- ratus. It will always show the true level of the water, as the foam will have no effect on the float. The slightest motion of the water in the boiler, when boiling, the pointer indicates on the dial. . The gauge being up- right and attached to the \ top of the boiler, drains ) itself, and consequently cannot freeze in cold wenther. this gauge being outside and above the boiler, and )0t immersed in the water, it does not be- come filled up or obstructed by sediment and requires no blowing out. The height of the water is shown by the movement of the pointer on the dial of the gauge by means of an iron rod lever, which works pointer and alarm valve, connected with the float in the boiler. . The alarm may be set to give the alarm at any height of water above the flues desired. NOTES AND QUERIES. C. W. C. asks: What is the relative tor- sion of common iron shafting, machine steel, cast steel, compressed steel, cold rolled shafting? A. The relative torsional values of the various kinds are estimated as follows: Ordinary turned shatting equals1; cold rolled shatting, 1.10; machinery steel shaft- ing, 3. We know of no tests of compressed steel.. E. J. Asks: Will you give in the Notes and Queries department the way to tell the horse-power of a steam engine? Multiply the area of the piston in square iuches by the average pressure on the piston in pounds per square inch; multiply this product by the number of feet of piston travel per revo- lution, and the product thus obtained by the number of revolutions per minute; divide the last product by 33,000, and the quotient will be the horse-power. W.S.P. writes: 1. Suppose asteam pipe, say 3 inches diameter, should have iron cast upon. its end, so as to close the end and come up on the pipe say 114 inches—the pipe hav- ing a thread cut ory being battered so as to ive a hold tothe casting—would the pipe eak steam at, say 100 to 125 pounds pres- sure?, If not, would the joint be durable? A. The chance of making a tight joint would not pay the trouble—it is very uncertain, and entirely ignored by those who make such joints as a business. Cut the threads and screw the caps on. In connection with the subject of ‘zinc in boilers, about which several inquiries have been recently made, a case lately re- ported is worthy of mention, in which it is stated that pieces of zinc had been put into a boiler to prevent incrustation by the feed water. After a few days the engine worked with difficulty and at last vaula not move. Upon examination, the piston wae found to be covered with a thick layer of copper. It was put into a lathe, and in some places which had been worn by use the layer was 8o thick that the turning was made in pure copper. The explanation given is that, the boiler being connected with the engine by copper tubes, particles of the zine which were carried with the steam formed with the tubes an immense number of galvanic couples. ‘The piston principally attracted the copper, both on account of its own con- tinual movement exercising an attraction of mass on the molecules, and of the heat which tacilitated their permanent deposit. An immense quantity of cedar is being hauled into Prescott for export to this side ‘he working parts of OUR NEW MONITORS. A humorous writer in the New York times says: “There is a vast amount ot popular misconception as to the true use of an American monitor. ‘lhe recent decision ot the naval authorities to give 48 hours’ notice before moving the monitor Nantucket from her present anchorage in the North River to the navy yard, in order that both rivers may be kept clear of other craft, ought to throw light on the mission of the moni- tors. ‘The Nantucket, like other vessels of her class, may be expected to yaw all over the river, owing to the difficulty of steering her. She will therefore run down, say seven vessels out of a possible ten. So far from detracting from her merits, this is one of her most valuable qualities as.a naval vessel, and render. her a most formidable war ship when in proper hands. Let us suppose that we are at war with England and the moni- tors are put in commission. People will say that in such circumstances the Miantonomah, the Nantucket and the rest of them would be useless, because they can neither fight nor run away. But have these rash critics reflected that the monitors may be captured by the enemy? In this case, would they not fight our battles in the most effectual possible way? For example, let us suppose that a hostile British fleet captures an American monitor and puts a prize crew on board her. ‘The first thing that the captured vessel would do would beto run down and sink the British fleet, or as many of the vessels composing it as might not take the alarm in time and steam away toa place of safety. If the fleet consists of ten vessels, the moni- tor will, as has been said, run down at Jeast seven of them. She will then start for Eng- l land in charge of her astenished prize crew, -and will infallibly sink ~ and drown them all the very first time she meets with bad weath- er. Now, what man-of-war is there that could inflict greater, injuries than these upon an en-" emy! If we had iron-elads in every respect the equals of the English iron-clads, it is very y improbable that any one of them would be able to sink more than two or three hostile ships. Whereas, should Eng- land send against us, say 49 first-class vessels, it would only ve unecessary tor us to permit them to cap- ture five monitors in order to render it mor- ally certain that 35 British ships would run be down.” STEALING TELEGRAPH WIRES. According toa report inan English ex- change which has just reached us, telegraph wires are now exposed” to anew danger which has. thus far never been thought of. It appears that quite recently two men were summoned before the mayistrates at Birm- ingham, England, for the commonplace offences of stealing wire. At first sight there is nothing surprising in this, s0 some may say, but when it is learned that this wire was a part of the British network of tele- graph wires, and that the whole telegraph service was totally disarranged by the theft, it will be admitted that it is somewhat aston- ishing. According to the report in question, the two men were engaged in excavating and laying down sewage pipes, and in the course of their excavations they came upon 33 telegraph wires in connection with all parts of the kingdom. ‘They evidently con- sidered that they had a luckey find, for they harnessed two horses to the wires and tore away 12 yards of each cable. ‘This wire was sold toa marine store dealer for a trifling sum, considering the labor of two men and a pair of horses. Naturally, after the break- age the utmost confusion prevailed at the telegraph officés, communication with most parts of the kingdom, besides Paris, New York and other places, being delayed for several hours, and the wires were not all repaired for two or three days. We have heard of telegraph wires being deranged by bears which. attacked the posts or by the ravages committed by the woodpecker which bores holes in the posts to reach the insects which he imagies are located in the interior. With submarine cables the teredo, the sword fish and other marine animals have proven destructive. At other times ships’ anchors have fouled and damaged them, and in many cases fishermen have maliciously cut the cables where thelr fishing tackle has caught them but to think that among the incidental dangers to which the wires are exposed should be the chance of their being cut and stolen by laborers is rather unusual, and it is to be hoped that the punishment inflicted will be of a sufficiently severe character to prevent the repetition of a similar practice. Cases of this kind have been recorded in Russia, where the peasants in passing along the roa'ls are known to have taken consider- able quantities of wire for domestie use. Considering the rather low level of education prevalent in these districts, the matter is not of 80 surprising a nature, but as above stated, itis only natural to suppose in more advanced countries occurrences of this kind should be of comparatively rare occurrence. $$$ Among lubricating oils, tine mineral oils stand first on the list of those which adhere well to metal surfaces, but are without per- ceptible molecular cohesion, Sperm oil vance second, neats foot third, and lard oil ourth, THE FRENCH AND AMERICAN SHIP- PING INTEREST. The bounty system adopted by the French Government some two years ago has given a decided impulse to. the shipping trade of that country. Late ‘statistics show nearly all the shipowning companies have added largely totheir fleets, and many new steam- ship someanies have been formed, ‘The French shipbuilding companies indeed have not been able to produce all the tonnage re- quired, although the premium in favor of French-built vessels give the latter a great advantage over vesgels bullt abroad, and the French shipbuilders have obtained a much higher rate for their tonnage than their British competitors. Nevertheless, a large number of steamers for various French com- panies have been and ure now being built on the Clyde. Exclusive of the coasting trade, the arrivals and departures at the va- rious ports of France during the first eight months of 1882 were represented by 13,261,- 000 register tons, against 10,550,000 tons same period in I877. The bounties to ship- ping, it may be remembered, were granted in respect to “deep water vessels,’’ those namely, engaged in the trade between France and her colonies and other countries beyond Europe. As regards the foreign carrying trade of France, the returns show that of the arrivals and clearances at all the ports during the first eight months of 1880 about 50 per cent, of the tonnage was under the French flag, whereas French carriage during the same period in 1882 had increased to about 60 per cent. On the other hand, in the trade in which no bounties are granted, foreign tonnage has increased, while French tonnage has remained about stationary. In other words, foreign vessels carry two-thirds of the merchandise which France sends to other European countries or receives from them in return. As a consequence, seyeral chambers of commerce, including that of Nantes, ‘have petitioned in favor of an ex- tension of the bounties to the trade with European countries. The working of the bountv systemin France will be watched with interest by American ship owners and shipping merchants, and if it continues to work well there it is possible that it will eventually be adopted here, though it is not at present in favor in this country, and is not likely to be tried until other expedients have been given achance. That something ought to be done without further unnecessary de- lay is apparent to all who pay much atten- tion to the statistics of our foreign commerce. ‘Thus, according to the Bureau of Statistics, the percentage of our foreign commerce car- ried in American vessele during the past fiscal year dropped to 15.5, the lowest point- reached in the history of the country. It has been falling regularly year by year since 1876, when it was-33.1 per cent. Before the civil war it was over 60 per cent. ‘The cir- cumstance that an American shipis at a dis- advantage in our’ own ports as well asin every foreign port in the world, as com- pared with Rritish or other foreign vessels, suggests that we ougl@ to begin by making it possible to sail ships at a profit; that done, it may appear tnat we can profitably build ships as well as sail them. BOOK NOTICES. We have before us a copy of the January number of the United States Official Postal Guide which we have just received from Messrs. Houghton, Mifflin & Co., of Boston. ‘The work contains alphabetical lists—of all postoffices in the United States, with county and State; of postoffices arranged by State; of postoffices arranged by States and counties, with the geographical position of the counties ; of the money order offices, domestic and international; of postoffices of the first, second and third class, with salaries; of counties, and a list ot letter-carrier offices; of Canadin money order offices; information about mailable matter; full directions about money. orders and registered letters; rates of foreign and domestic postage; all needed information about postal matters. Lists ot streets, avenues and money order offices or stations in New York and Chicago are given, which show where money orders addressed to persons residing in those cities should be made payable. ‘They will be tound of great assistance to parties sending money orders to these places. A supplementary number is issued monthly, containing the latest changes in postoffices, postal laws, etc. Terms: January number, in paper, $1; cloth, $1.50. Per year, in paper, $1.50, in cloth, $2. For sale at the postoffice, and by booksellers and newsdealers. THERE’S A LIMIT TO EVERYTHING. “There, isn’t that just too provoking for anything,” exclaimed Mrs. Smiftkins throw- ing as:de the paper with a look of angry dis- appointment. ‘[t’salways the way though; I never get interested in a newspaper article unless itends up with ‘Blank & Co.’s soft sonp cure for billiousness or some other pat- ent medicine advertisment.’ Now that sort of advertising is all wrong. Mrs. Smiffkins would never have been vexed had she read Dr. Swayne’s ten line notice of his ointment for skin diseases. ‘ The Green Bay Advocate announces that the barge W. L. Brown, Captain Spafford, is to be fitted up for passenger traffic and put upon the “bay route,’”? between Green Bay and Manistique