Chapter VIII: MISCELLANEOUS.--Puerta del Sol, Madrid, Spain.--With (3)

A great difference in chemical composition of the liquid was attended by a considerable change in the order of the volta-tension series, and the differences of such order in two similar liquids, such as solutions of hydric chloride and potassic chloride, were much greater than those produced in either of those liquids by a difference of 100° F. of temperature. Difference of strength of solution, like difference of composition or of temperature, altered the order of such series with nearly every liquid; and the amount of such alteration by an increase of four or five times in the strength of the liquid was rather less than that caused by a difference of 100° F. of temperature. While also a variation of strength of liquid caused only a moderate amount of change of order in the volta-tension series, it produced more than three times that amount of change in the thermo-electric tension series. The usual effect of increasing the strength of the liquid upon the volta-electromotive force was to considerably increase it, but its effect upon the thermo-electro-motive force was to largely decrease it. The degree of potential of a metal and liquid thermo-couple was not always exactly the same at the same temperature during a rise as during a fall of temperature; this is analogous to the variations of melting and solidifying points of bodies under such conditions, and also to that of supersaturation of a liquid by a salt, and is probably due to some hinderance to change of molecular movement.

The rate of ordinary chemical corrosion of each metal varied in every different liquid; in each solution also it differed with every different metal. The most chemically positive metals were usually the most quickly corroded, and the corrosion of each metal was usually the fastest with the most acid solutions. The rate of corrosion at any given temperature was dependent both upon the nature of the metal and upon that of the liquid, and was limited by the most feebly active of the two, usually the electrolyte. The order of rate of corrosion of metals also differed in every different liquid. The more dissimilar the chemical characters of two liquids, the more diverse usually was the order of rapidity of corrosion of a series of metals in them. The order of rate of simple corrosion in any of the liquids examined differed from that of chemico-electric and still more from that of thermo-electric tension. Corrosion is not the cause of thermo-electric action of metals in liquids.

Out of fifty-eight cases of rise of temperature the rate of ordinary corrosion was increased in every instance except one, and that was only a feeble exception--the increase of corrosion from 60° to 160° F. with different metals was extremely variable, and was from 1.5 to 321.6 times. Whether a metal increased or decreased in thermo-electromotive force by being heated, it increased in rapidity of corrosion. The proportions in which the most corroded metal was also the most thermo-electro-positive one was 65.57 per cent. in liquids at 60° F., and 69.12 in the same liquids at 160° F.; and the proportion in which it was the most chemico-electro-positive at 60 F. was 84.44 per cent, and at 160° F. 80.77 per cent. The proportion of cases therefore in which the most chemico-electro-negative metal was the most corroded one increased from 15.56 to 19.23 per cent, by a rise of temperature of 100° F. Comparison of these proportions shows that corrosion usually influenced in a greater degree chemico-electric rather than thermo-electric actions of metals in liquids. Not only was the relative number of cases in which the volta-negative metal was the most corroded increased by rise of temperature, but also the average relative loss by corrosion of the negative to that of the positive one was increased from 3.11 to 6.32.

The explanation most consistent with all the various results and conclusions is a kinetic one: That metals and electrolytes are throughout their masses in a state of molecular vibration. That the molecules of those substances, being frictionless bodies in a frictionless medium, and their motion not being dissipated by conduction or radiation, continue incessantly in motion until some cause arises to prevent them. That each metal (or electrolyte), when unequally heated, has to a certain extent an unlike class of motions in its differently heated parts, and behaves in those parts somewhat like two metals (or electrolytes), and those unlike motions are enabled, through the intermediate conducting portion of the substance, to render those parts electro-polar. That every different metal and electrolyte has a different class of motions, and in consequence of this, they also, by contact alone with each other at the same temperature, become electro-polar. The molecular motion of each different substance also increases at a different rate by rise of temperature.

This theory is equally in agreement with the chemico-electric results. In accordance with it, when in the case of a metal and an electrolyte, the two classes of motions are sufficiently unlike, chemical corrosion of the metal by the liquid takes place, and the voltaic current originated by inherent molecular motion, under the condition of contact, is maintained by the portions of motion lost by the metal and liquid during the act of uniting together. Corrosion therefore is an effect of molecular motion, and is one of the modes by which that motion is converted into and produces electric current.

In accordance with this theory, if we take a thermo-electric pair consisting of a non-corrodible metal and an electrolyte (the two being already electro-polar by mutual contact), and heat one of their points of contact, the molecular motions of the heated end of each substance at the junction are altered; and as thermo-electric energy in such combinations usually increases by rise of temperature, the metal and liquid, each singly, usually becomes more electro polar. In such a case the unequally heated metal behaves to some extent like two metals, and the unequally heated liquid like two liquids, and so the thermo-electric pair is like a feeble chemico-electric one of two metals in two liquids, but without corrosion of either metal. If the metal and liquid are each, when alone, thermo-electro-positive, and if, when in contact, the metal increases in positive condition faster than the liquid by being heated, the latter appears thermo-electro-negative, but if less rapidly than the liquid, the metal appears thermo-electro-negative.

As also the proportion of cases is small in which metals that are positive in the ordinary thermo-electric series of metals only become negative in the metal and liquid ones (viz., only 73 out of 286 in weak solutions, and 48 out of the same number in strong ones), we may conclude that the metals, more frequently than the liquids, have the greatest thermo-electric influence, and also that the relative largeness of the number of instances of thermo-electro-positive metals in the series of metals and liquids, as in the series of metals only, is partly a consequence of the circumstance that rise of temperature usually makes substances--metals in particular--electro-positive. These statements are also consistent with the view that the elementary substances lose a portion of their molecular activity when they unite to form acids or salts, and that electrolytes therefore have usually a less degree of molecular motion than the metals of which they are partly composed.

The current from a thermo-couple of metal and liquid, therefore, may be viewed as the united result of difference of molecular motion, first, of the two junctions, and second, of the two heated (or cooled) substances; and in all cases, both of thermo- and chemico-electric action, the immediate true cause of the current is the original molecular vibrations of the substances, while contact is only a static permitting condition. Also that while in the case of thermo-electric action the sustaining cause is molecular motion, supplied by an external source of heat, in the case of chemico-electric action it is the motion lost by the metal and liquid when chemically uniting together. The direction of the current in thermo-electric cases appears to depend upon which of the two substances composing a junction increases in molecular activity the fastest by rise of temperature, or decreases the most rapidly by cooling.

* * * * *

AIR REFRIGERATING MACHINE.

Messrs. J. & E. Hall, Dartford, exhibit at the International Health Exhibition, London, in connection with a cold storage room, two sizes of Ellis' patent air refrigerator, the larger one capable of delivering 5,000 cubic feet of cold air per hour, when running at a speed of 150 revolutions per minute; and the smaller one 2,000 cubic feet of cold air per hour, at 225 revolutions per minute. The special features in these machines are the arrangement of parts, by which great compactness is secured, and the adoption of flat slides for the compressor, instead of the ordinary beat valves, which permits of a high rate of revolution without the objectionable noise which is caused by clacks beating on their seats. The engraving shows the general arrangement of the apparatus. Figs. 1 to 4 show details of the compression and expansion valves, which are ordinary flat slides, partly balanced, and held up to their faces by strong springs from behind. The steam, compression, and expansion cylinders are severally bolted to the end of a strong frame, which though attached to the cooler box does not form part of it, the object being to meet the strains between the cylinders and shaft in as direct a manner as possible without allowing them to act on the cooler casting. Each cylinder is double acting, the pistons being coupled to the shaft by three connecting rods, the two outer ones working upon crank pins fixed to overhung disks, and the center one on a crank formed in the shaft. The slide valves for all the cylinders are driven from two weigh shafts, the main valve shaft being actuated by a follow crank, and the expansion and cut off valves from the crosshead pin of the compressor. The machines may be used either in the vertical position as exhibited, or may be fixed horizontally; and it is stated that the construction is such as to admit of speeds of 200 and 300 revolutions per minute respectively for the larger and smaller machines, under which conditions the delivery of cold air may be taken at about 7,000 and 2,600 cubic feet per hour. Messrs. Hall also make this class of refrigerator without the steam cylinder, and arranged to be driven by a belt from a gas engine or any existing motive power.

* * * * *

A GAS RADIATOR AND HEATER.

There is now being introduced into Germany a gas radiator and heater, the invention of Herr Wobbe. It consists, as will be seen in engraving above, of a series of vertical U-shaped pipes, of wrought iron, 50 millimeters (2 inches) in diameter. The two legs of the U are of unequal length; the longer being about 5 feet, and the shorter 3 feet (exclusive of the bend at the top). Beneath the open end of the shorter leg of each pipe is placed a burner, attached to a horizontal gas-pipe, which turns upon an axis. The object of having this pipe rotate is to bring the burners into an inclined position--shown by the dotted lines in Fig. 2--for lighting them. On turning them back to the vertical position, the heated products of combustion pass up the shorter tube and down the longer, where they enter a common receptacle, from which they pass into the chimney or out of doors. Surrounding the pipes are plates of sheet iron, inclined at the angle shown in Fig. 2. The object of the plates is to prevent the heated air of the room from passing up to the ceiling, and send it out into the room. To prevent any of the pipes acting as chimneys, and bringing the products of combustion back into the room, as well as to avoid any back-pressure, a damper is attached to the outlet receptacle. The heated gas becomes cooled so much (to about 100° Fahr.) that water is condensed and precipitated, and collects in the vessel below the outlet. Each burner has a separate cock, by which it may be kept closed, half-open, or open. To obviate danger of explosion, there is a strip of sheet iron in front of the burners, which prevents their being lighted when in a vertical position; so that, in case any unburned gas gets into the pipes, it cannot be ignited, for the burners can only be lighted when inclined to the front. In starting the stove the burners are lighted, in the inclined position; the chain from the damper pulled up; the burners set vertical; and, as soon as they are all drawing well into the tubes, the damper is closed. If less heat is desired, the cocks are turned half off. It is not permissible to entirely extinguish some of the burners, unless the unused pipes are closed to prevent the products of combustion coming back into the room. The consumption of gas per burner, full open, with a pressure of 8/10, is said to be only 4-3/8 cubic feet per hour.

* * * * *

CONCRETE WATER PIPES.

Concrete water pipes of small diameter, according to a foreign contemporary, are used in parts of France, notably for water mains for the towns of Coulommiers and Aix-en-Provence. The pipes were formed of concrete in the trench itself. The mould into which the concrete was stamped was sheet iron about two yards in length. The several pipes were not specially joined to each other, the joints being set with mortar. The concrete consisted of three parts of slow setting cement and three parts of river sand, mixed with five parts of limestone debris. The inner diameter of the pipes was nine inches; their thickness, three inches. The average fall is given at one in five hundred; the lowest speed of the current at one foot nine inches per second. To facilitate the cleaning of the pipes, man-holes are constructed every one hundred yards or so, the sides of which are also made of concrete. The trenches are about five feet deep. The work was done by four men, who laid down nearly two hundred feet of pipe in a working day; the cost was about ninety-three cents per running yard. It is claimed as an advantage for the new method that the pipes adhere closely to the inequalities of the trench, and thus lie firmly on the ground. When submitted to great pressure, however, they have not proved effective, and the method, consequently, is only suitable for pipes in which there is no pressure, or only a very trifling one.

* * * * *

THE SELLERS STANDARD SYSTEM OF SCREW THREADS, NUTS, AND BOLT HEADS.

_____________________________________________________
| |
| SCREW THREADS. |
|_____________________________________________________|
| | | | | |
| Diam. |Threads | Diameter | Area of | Width |
| of | per | at root of | Bolt at | of |
| Screw. | inch. | Thread. | root of | Flat. |
| | | | Thread. | |
|________|________|_________________|_________|_______|
| | | | | | |
| 1/4 | 20 | .185 | 13/64 | .026 | .0062 |
| 5/16 | 18 | .240 | 15/64 | .045 | .0074 |
| 3/8 | 16 | .294 | 19/64 | .067 | .0078 |
| 7/16 | 14 | .344 | 11/32 | .092 | .0089 |
| 1/2 | 13 | .400 | 13/32 | .125 | .0096 |
| 9/16 | 12 | .454 | 29/64 | .161 | .0104 |
| 5/8 | 11 | .507 | 33/64 | .201 | .0113 |
| 3/4 | 10 | .620 | 5/8 | .301 | .0125 |
| 7/8 | 9 | .731 | 47/64 | .419 | .0138 |
| | | | | | |
| 1 | 8 | .837 | 27/32 | .550 | .0156 |
| 1-1/8 | 7 | .940 | 15/16 | .693 | .0178 |
| 1-1/4 | 7 | 1.065 | 1- 1/16 | .890 | .0178 |
| 1-3/8 | 6 | 1.160 | 1- 5/32 | 1.056 | .0208 |
| 1-1/2 | 6 | 1.284 | 1- 9/32 | 1.294 | .0208 |
| 1-5/8 | 5-1/2 | 1.389 | 1-25/64 | 1.515 | .0227 |
| 1-3/4 | 5 | 1.491 | 1-31/64 | 1.746 | .0250 |
| 1-7/8 | 5 | 1.616 | 1-39/64 | 2.051 | .0250 |
| | | | | | |
| 2 | 4-1/2 | 1.742 | 1-23/32 | 2.301 | .0277 |
| 2-1/4 | 4-1/2 | 1.962 | 1-31/32 | 3.023 | .0277 |
| 2-1/2 | 4 | 2.176 | 2-11/64 | 3.718 | .0312 |
| 2-3/4 | 4 | 2.426 | 2-27/64 | 4.622 | .0312 |
| | | | | | |
| 3 | 3-1/2 | 2.629 | 2- 5/8 | 5.428 | .0357 |
| 3-1/4 | 3-1/2 | 2.879 | 2- 7/8 | 6.509 | .0357 |
| 3-1/2 | 3-1/4 | 3.100 | 3- 3/32 | 7.547 | .0384 |
| 3-3/4 | 3 | 3.317 | 3- 5/16 | 8.614 | .0413 |
| | | | | | |
| 4 | 3 | 3.567 | 3- 9/16 | 9.993 | .0413 |
| 4-1/4 | 2-7/8 | 3.798 | 3-51/64 | 11.329 | .0435 |
| 4-1/2 | 2-3/4 | 4.028 | 4- 1/32 | 12.742 | .0454 |
| 4-3/4 | 2-5/8 | 4.256 | 4- 1/4 | 14.226 | .0476 |
| | | | | | |
| 5 | 2-1/2 | 4.480 | 4-31/64 | 15.763 | .0500 |
| 5-1/4 | 2-1/2 | 4.730 | 4-47/64 | 17.570 | .0500 |
| 5-1/2 | 2-3/8 | 4.953 | 4-61/64 | 19.267 | .0526 |
| 5-3/4 | 2-3/8 | 5.203 | 5-13/64 | 21.261 | .0526 |
| 6 | 2-1/4 | 5.423 | 5-27/64 | 23.097 | .0555 |
|________|________|_________________|_________|_______|
_____________________________________________________________
| |
| NUTS. |
|___________________ __________________________________________|
| | | | | | |
| Short | Short | Long | Long | Thick- | Thick- |
| Diam. | Diam. | Diam. | Diam. | ness | ness |
| Rough. | Finish. | Rough. | Rough. | Rough. | Finish. |
| | | | | | |
| (Hex.) | (Hex.) | (Hex.) | (Square) | | |
|_________|_________ |__________|__________|_________|_________|
| | | | | | |
| 1/2 | 7/16 | 37/64 | 7/10 | 1/4 | 3/16 |
| 19/32 | 17/32 | 11/16 | 10/12 | 5/16 | 1/4 |
| 11/16 | 5/8 | 51/64 | 63/64 | 3/8 | 5/16 |
| 25/32 | 23/33 | 9/10 | 1- 7/64 | 7/16 | 3/8 |
| 7/8 | 13/16 | 1 | 1-15/64 | 1/2 | 7/16 |
| 31/32 | 29/32 | 1- 1/8 | 1-23/64 | 9/16 | 1/2 |
| 1-1/16 | 1 | 1- 7/32 | 1- 1/2 | 5/8 | 9/16 |
| 1-1/4 | 1-3/16 | 1- 7/16 | 1-49/64 | 3/4 | 11/16 |
| 1-7/16 | 1-3/8 | 1-21/32 | 2- 1/32 | 7/8 | 13/16 |
| | | | | | |
| 1- 5/8 | 1-9/16 | 1- 7/8 | 2-19/64 | 1 | 15/16 |
| 1-13/16| 1- 3/4 | 2- 5/32 | 2- 9/16 | 1-1/8 | 1- 1/16 |
| 2 | 1-15/16 | 2- 5/16 | 2-53/64 | 1-1/4 | 1- 3/16 |
| 2- 3/16| 2- 1/8 | 2-17/32 | 3- 3/32 | 1-3/8 | 1- 5/16 |
| 2- 3/8 | 2- 5/16 | 2- 3/4 | 3-23/64 | 1-1/2 | 1- 7/16 |
| 2- 9/16| 2- 1/2 | 2-31/32 | 3- 5/8 | 1-5/8 | 1- 9/16 |
| 2- 3/4 | 2-11/16 | 3- 3/16 | 3-57/64 | 1-3/4 | 1-11/16 |
| 2-15/16| 2- 7/8 | 3-13/32 | 4- 5/32 | 1-7/8 | 1-13/16 |
| | | | | | |
| 3-1/8 | 3- 1/16 | 3- 5/8 | 4-27/64 | 2 | 1-15/16 |
| 3-1/2 | 3- 7/16 | 4- 1/16 | 4-61/64 | 2-1/4 | 2- 3/16 |
| 3-7/8 | 3-13/16 | 4- 1/2 | 5-31/64 | 2-1/2 | 2- 7/16 |
| 4-1/4 | 4- 3/16 | 4-29/32 | 6 | 2-3/4 | 2-11/16 |
| | | | | | |
| 4-5/8 | 4- 9/16 | 5- 3/8 | 6-17/32 | 3 | 2-15/16 |
| 5 | 4-15/16 | 5-13/16 | 7- 1/16 | 3-1/4 | 3- 3/16 |
| 5-3/8 | 5- 5/16 | 6- 7/32 | 7-39/64 | 3-1/2 | 3- 7/16 |
| 5-3/4 | 5-11/16 | 6-21/32 | 8- 1/8 | 3-3/4 | 3-11/16 |
| | | | | | |
| 6-1/8 | 6- 1/16 | 7- 3/32 | 8-41/64 | 4 | 3-15/16 |
| 6-1/2 | 6- 7/16 | 7- 9/16 | 9- 3/16 | 4-1/4 | 4- 3/16 |
| 6-7/8 | 6-13/16 | 7-31/32 | 9- 3/4 | 4-1/2 | 4- 7/16 |
| 7-1/4 | 7- 3/16 | 8-13/32 | 10- 1/4 | 4-3/4 | 4-11/16 |
| | | | | | |
| 7-5/8 | 7- 9/16 | 8-27/32 | 10-49/64 | 5 | 4-15/16 |
| 8 | 7-15/16 | 9- 9/32 | 11-23/64 | 5-1/4 | 5- 3/16 |
| 8-3/8 | 8- 5/16 | 9-23/32 | 11- 7/8 | 5-1/2 | 5- 7/16 |
| 8-3/4 | 8-11/16 | 10- 5/32 | 12- 3/8 | 5-3/4 | 5-11/16 |
| 9-1/8 | 9- 1/16 | 10-19/32 | 12-15/16 | 6 | 5-15/16 |
|_________|__________|__________|__________|_________|_________|
_____________________________________________________________
| |
| BOLT HEADS. |
|_____________________________________________________________|
| | | | | | |
| Short | Short | Long | Long | Thick- | Thick- |
| Diam. | Diam. | Diam. | Diam. | ness | ness |
| Rough. | Finish. | Rough. | Rough. | Rough. | Finish. |
| | | | | | |
| (Hex.) | (Hex.) | (Hex.) | (Square) | | |
|_________|_________|__________|__________|_________|_________|
| | | | | | |
| 1/2 | 7/16 | 37/64 | 7/10 | 1/4 | 3/16 |
| 19/32 | 17/32 | 11/16 | 10/12 | 19/64 | 1/4 |
| 11/16 | 5/8 | 51/64 | 63/64 | 11/32 | 5/16 |
| 25/32 | 23/32 | 9/16 | 1-7/64 | 25/64 | 3/8 |
| 7/8 | 13/16 | 1 | 1-15/64 | 7/16 | 7/16 |
| 31/32 | 29/32 | 1- 1/8 | 1-23/64 | 31/64 | 1/2 |
| 1- 1/16 | 1 | 1- 7/32 | 1- 1/2 | 17/32 | 9/16 |
| 1- 1/4 | 1- 3/16 | 1- 7/16 | 1-49/64 | 5/8 | 11/16 |
| 1- 7/16 | 1- 3/8 | 1-21/32 | 2- 1/32 | 23/32 | 13/16 |
| | | | | | |
| 1- 5/8 | 1- 9/16 | 1- 7/8 | 2-19/64 | 13/16 | 15/16 |
| 1-13/16 | 1- 3/4 | 2- 5/32 | 2- 7/16 | 29/32 | 1- 1/16 |
| 2 | 1-15/16 | 2- 5/16 | 2-53/64 | 1 | 1- 3/16 |
| 2- 3/16 | 2- 1/8 | 2-17/32 | 3- 3/32 | 1- 3/32 | 1- 5/16 |
| 2- 3/8 | 2- 5/16 | 2- 3/4 | 3-23/64 | 1- 3/16 | 1- 7/16 |
| 2- 9/16 | 2- 1/2 | 2-31/32 | 3- 5/8 | 1- 9/32 | 1- 9/16 |
| 2- 3/4 | 2-11/16 | 3- 3/16 | 3-57/64 | 1- 3/8 | 1-11/16 |
| 2-15/16 | 2- 7/8 | 3-13/32 | 4- 5/32 | 1-15/32 | 1-13/16 |
| | | | | | |
| 3- 1/8 | 3- 1/16 | 3- 5/8 | 4-27/64 | 1- 9/16 | 1-15/16 |
| 3- 1/2 | 3- 7/16 | 4- 1/16 | 4-61/64 | 1- 3/4 | 2- 3/16 |
| 3- 7/8 | 3-13/16 | 4- 1/2 | 5-31/64 | 1-15/16 | 2- 7/16 |
| 4- 1/4 | 4- 3/16 | 4-29/32 | 6 | 2- 1/8 | 2-11/16 |
| | | | | | |
| 4- 5/8 | 4- 9/16 | 5- 3/8 | 6-17/32 | 2- 5/16 | 2-15/16 |
| 5 | 4-15/16 | 5-13/16 | 7- 1/16 | 2- 1/2 | 3- 3/16 |
| 5- 3/8 | 5- 5/16 | 6- 7/32 | 7-39/64 | 2-11/16 | 3- 7/16 |
| 5- 3/4 | 5-11/16 | 6-21/32 | 8- 1/8 | 2- 7/8 | 3-11/16 |
| | | | | | |
| 6- 1/8 | 6- 1/16 | 7- 3/32 | 8-41/64 | 3- 1/16 | 3-15/16 |
| 6- 1/2 | 6- 7/16 | 7- 9/16 | 9- 3/16 | 3- 1/4 | 4- 3/16 |
| 6- 7/8 | 6-13/16 | 7-31/32 | 9- 3/4 | 3- 7/16 | 4- 7/16 |
| 7- 1/4 | 7- 3/16 | 8-13/32 | 10- 1/4 | 3- 5/8 | 4-11/16 |
| | | | | | |
| 7- 5/8 | 7- 9/16 | 8-27/32 | 10-49/64 | 3-13/16 | 4-15/16 |
| 8 | 7-15/16 | 9- 9/32 | 11-23/64 | 4 | 5- 3/16 |
| 8- 3/8 | 8- 5/16 | 9-23/32 | 11- 7/8 | 4- 3/16 | 5- 7/16 |
| 8- 3/4 | 8-11/16 | 10- 5/32 | 12- 3/8 | 4- 3/8 | 5-11/16 |
| 9- 1/8 | 9- 1/16 | 10-19/32 | 12-15/16 4- 9/16 | 5-15/16 |
|_________|_________|__________|__________|_________|_________|

The dimensions given for diameter at root of threads are also those for diameter of hole in nuts and diameter of lap drills. All bolts and studs 3/4 in. diameter and above, screwed into boilers, have 12 threads per inch, sharp thread, a taper of 1/16 in. per 1 inch; tap drill should be 9/64 in. less than normal diameter of bolts.

The table is based upon the following general formulæ for certain dimensions:

Short diam. rough nut or head = 11/2 diam. of bolt + 1/8.
" finished nut or head = 11/2 diam. of bolt + 1/16.
Thickness rough nut = diameter of bolt.
Thickness finished nut = diameter of bolt - 1/16.
Thickness rough head = 1/2 short diameter.
Thickness finished head = diameter of bolt - 1/16.

* * * * *

AN ENGLISH RAILWAY FERRY BOAT.

The illustrations above represent a double screw steam ferry boat for transporting railway carriages, vehicles, and passengers, etc., designed and constructed by Messrs. Edwards and Symes, of Cubitt Town, London. The hull is constructed of iron, and is of the following dimensions: Length 60 ft.; beam 16 ft.; over sponsons 25 ft. The vessel was fitted with a propeller, rudder, and steering gear at each end, to enable it to run in either direction without having to turn around. The boat was designed for the purpose of working the train service across the bay of San Juan, in the island of Puerto Rico, and for this purpose a single line of steel rails, of meter gauge, is laid along the center of the deck, and also along the hinged platforms at each end. In the engraving these platforms are shown, one hoisted up, and the other lowered to the level of the deck. When the boat is at one of the landing stages, the platform is lowered to the level of the rails on the pier, and the carriages and trucks are run on to the deck by means of the small hauling engine, which works an endless chain running the whole length of the deck. The trucks, etc., being on board, the platform is raised by means of two compact hand winches worked by worm and worm-wheels in the positions shown; thus these two platforms form the end bulwarks to the boat when crossing the bay. On arriving at the opposite shore the operation is repeated, the other platform is lowered, and the hauling engine runs the trucks, etc., on to the shore. With a load of 25 tons the draught is 4 ft.

The seats shown on the deck are for the convenience of foot passengers, and the whole of the deck is protected from the sun of that tropical climate by a canvas awning. The steering of the vessel is effected from the bridge at the center, which extends from side to side of the vessel, and there are two steering wheels with independent steering gear for each end, with locking gear for the forward rudder when in motion. The man at the wheel communicates with the engineer by means of a speaking tube at the wheel. There is a small deck house for the use of deck stores, on one side of which is the entrance to the engine room. The cross battens, shown between the rails, are for the purpose of horse traffic, when horses are used for hauling the trucks, or for ordinary carts or wagons. The plan below deck shows the arrangement of the bulkheads, with a small windlass at each end for lifting the anchors, and a small hatch at each side for entrance to these compartments. The central compartment contains the machinery, which consists of a pair of compound surface condensing engines, with cylinders 11 in. and 20 in. in diameter; the shafting running the whole length of the vessel, with a propeller at each end. Steam is generated in a steel boiler of locomotive form, so arranged that the funnel passes through the deck at the side of the vessel; and it is designed for a working pressure of 100 lb. per square inch. This boiler also supplies steam for the small hauling engine fixed on the bulkhead. Light to this compartment is obtained by means of large side scuttles along each side of the boat and glass deck lights, and the iron grating at the entrance near the deck house. This boat was constructed in six pieces for shipment, and the whole put together in the builders' yard. The machinery was fixed, and the engine driven by steam from its own boiler, then the whole was marked and taken asunder, and shipped to the West Indies, where it was put together and found to answer the purpose intended.--_Engineering._

* * * * *

[For THE SCIENTIFIC AMERICAN.]

THE PROBLEM OF FLIGHT, AND THE FLYING MACHINE.

As a result of reading the various communications to the SCIENTIFIC AMERICAN and SUPPLEMENT, and _Van Nostrand's Engineering Magazine_, including descriptions of proposed and tested machines, and the reports of the British Aeronautical Society, the writer of the following concludes:

That, as precedents for the construction of a successful flying machine, the investigation of some species of birds as a base of the principles of all is correct only in connection with the species and habits of the bird; that the _general mechanical principles_ of flight applicable to the _operation_ of the _same unit_ of wing in _all_ species are alone applicable to the flying machine.

That these principles of _operation_ do not demand the principles of _construction_ of the bird.

That as the wing is in its stroke an arc of a screw propeller's operation, and in its angle a screw propeller blade, its animal operation compels its reciprocation instead of rotation.

That the swifter the wing beat, the more efficient its effect per unit of surface, the greater the load carried, and the swifter the flight.

That the screw action being, in full flight, that of a screw propeller whose axis of rotation forms a slight angle with the vertical, the distance of flight per virtual "revolution" of "screw" wing far exceeds the pitch distance of said "screw."

That consequently a bird's flight answers to an iceboat close hauled; the wing _force_ answering to the _wind_, the wing _angle_ to the _sail_, the bird's _weight_ to the leeway fulcrum of the _ice_, and the passage across direction of the _wing_ flop to the fresh _moving_ "inertia" of the wind, both yielding a maximum of force to bird or iceboat.

That the speed of _reciprocation_ of a fly's _wing_ being equivalent to a _screw rotation_ of 9,000 per minute, proves that a _screw_ may be run at this speed without losing efficiency by centrifugal vacuum.

That as the _object_ of wing or screw is to mount upon the inertia of the particles of a mobile fluid, and as the rotation of steamship propellers in water--a fluid of many times the inertia of air--is _already_ in _excess_ of the highest speed heretofore tried in the propellers of moderately successful flying machines, it is plain that the speed employed in _water_ must be many times exceeded in _air_.

That with a _sufficient_ speed of rotation, the supporting power of the inertia of air must _equal_ that of _water_.

That as mere speed of rotation of propeller _shaft_, minus blades, must absorb but a small proportion of power of engine, the addition of blades will not cause more resistance than that actually encountered from inertia of air.

That this must be the measure of load lifted.

That without _slip_ of screw, the actual _power_ expended, will be little in _excess_ of that required to support the machine in _water_, with a slower rotation of screw.

That in case the same _power_ is expended in water or air, the only difference will lie in the sizes and speed of engines or screws.

That the _greater_ the speed, the _less_ weight of engine, boiler, and screw must be, and the stronger their construction.

That, in consequence, solid metal worked down, instead of bolts and truss work, must be used.

That as the bird wing is a screw in action, and acts _directly_ between the inertias of the load and the air, the position and operation of the screw, to the load, must imitate it.

That, in consequence, machines having wing planes, driven _against_ one inertia of air by screws acting in the line, of flight against another inertia of air, lose fifty per cent. of useful effect, besides exposing to a head wind the cross section of the stationary screw wing planes and the rotating screw discs; and supporting the dead weight of the wing planes, and having all the screw slip in the line of flight, and carrying slow and heavy engines.

That as a result of these conclusions, the supporting and propelling power should be expressed in the rotation of screws combining both functions, the position of whose planes of rotation to a fixed horizontal line of direction determines the progress and speed of machine upon other lines.

That the whole weight carried by the screws should be at all times exactly below the center of gravity of the plane of support, whether it be horizontal or inclined.

That while the _permanently_ positioned weight, such as the engines, frame, holding screws, etc., may be rigidly connected to or around the screw plane of support, the variable positioned weight, such as the passenger and the car, should be connected by a _flexible joint_ to the said plane of support.

Consequently, the car may oscillate without altering its weight position under center of supporting plane, thus avoiding an involuntary alteration of speed or direction of flight.

That to steer a machine so constructed, it is merely necessary to move the point of attachment of car to _machine_ proper, out of the center of plane of support in the desired direction, and thus cause the plane of support or rotation of propellers to incline in that direction.

That the reservoir of power, the boiler, etc., should be placed in the _car_, and steam carried to engines through joint connecting car with machine.

That at present material exists, and power also, of sufficient lightness and strength to admit of a machine construction capable of a limited successful flight in any fair wind and direction.

That such _machine_ once built, the finding of a _power_ for long flights will be easy, if not already close at hand in _electricity_.

That the _easiest_ design for such _actual machine_ should be adopted, leaving the adaptation of the principles involved to the making of more perfect machines, to a time after the success of the _first_.

That such design may be a propeller, and its engine at each end of a steel frame tube, supporting tube horizontally, a car to be supported by a universal joint from center of said tube, and the joint apparatus movable along the tube or a short distance transverse to it, to alter position of center of gravity.

That the machine so built might traverse the water as well as air.

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THE LONGHAIRED POINTER MYLORD.

Pointers are trained to search for game, and to indicate that they have found the same by standing motionless in front of it, and, when it has been shot, to carry the game to the huntsman. Several kinds of pointers are known, such as smooth, longhaired, and bushyhaired pointers. The smoothhaired pointers are better for hunting on high land, whereas the longhaired or bushyhaired dogs are better for low, marshy countries, crossed by numerous streams, etc. Mylord, the dog represented in the annexed cut taken from the _Illustrirte Zeitung_, is an excellent specimen of the longhaired pointer, and is owned by Mr. G. Borcher, of Braunschweig, Germany.

The longhaired pointer is generally above the medium size, powerful, somewhat longer than the normal dog, the body is narrower and not quite as round as that of the smoothhaired dog, and the muscles of the shoulders and hind legs are not as well developed and not as prominent. The head and neck are erect, the head being specially long, and the tail is almost horizontal to the middle, and then curves upward slightly. The long hair hangs in wavy lines on both sides of his body. The expression of his face is intelligent, bright, and good-natured, and his step is light and almost noiseless.

The pointer is specially valuable, as it can be employed for many different purposes; he is an excellent dog for the woods, for the woodsman and hunter who uses only one dog for different kinds of game. The intelligence of the German pointer is very great, but he does not develop as rapidly as the English dog, which has been raised for generations for one purpose only. The German pointer hunts very slowly, but surely. It is not difficult to train this dog, but he cannot be trained until he has reached a certain age.

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LUNAR HEAT.

By Professor C.A. YOUNG.

One of the most interesting inquiries relating to the moon is that which deals with the heat she sends us, and the probable temperature of her surface. The problem seems to have been first attacked by Tschirnhausen and La Hire, about 1700; and they both found, that even when the moon's rays were concentrated by the most powerful burning-lenses and mirrors they could obtain, its heat was too small to produce the slightest perceptible effect on the most delicate thermometers then known. For more than a hundred years, this was all that could be made out, though the experiment was often repeated.

It was not until 1831 that Melloni, with his newly-invented "thermopile," [1] succeeded in making the lunar heat sensible; and in 1835, taking his apparatus to the top of Vesuvius, he obtained not only perceptible, but measurable, results, getting a deviation of four or five divisions of his galvanometer.

[Footnote 1: Probably most of our readers know that the
thermopile consists of a number of little bars of two different
metals, connected in pairs, and having the ends joined in a
conducting circuit with a galvanometer. If, now, one set of the
junctures is heated more than the other set, a current of
electricity will be generated, which will affect the
galvanometer. The bars are usually made of bismuth and antimony
though iron and German silver answer pretty well. They are
commonly about half or three-quarters of an inch long, and about
half as large as an ordinary match. The "pile" is made of from
fifty to a hundred such bars packed closely, but insulated by
thin strips of mica, except just at the soldered junctions. With
an instrument of this kind and a very delicate galvanometer,
Professor Henry found that the heat from a person's face could be
perceived at a distance of several hundred feet. There is
however, some doubt whether he was not mistaken in respect to
this extreme sensitiveness.]

Others repeated the experiment several times between this time and 1856, with more or less success; but, so far as I know, the first quantitative result was that obtained in 1856 by Piazzi Smyth during his Teneriffe expedition. On the top of the mountain, at an elevation of ten thousand feet, he found that the moon's rays affected his thermopile to the same extent as a standard candle ten feet away. Marie Davy has since shown that this corresponds to a heating effect of about 1/1300 of a Centigrade degree.

The subject was resumed in 1868 by Lord Rosse in Ireland; and a long series of observations, running through several years, was made by the aid of his three-foot reflector (not the great _six_-foot instrument, which is too unwieldy for such work). The results of his work have, until very recently, been accepted as authoritative. It should be mentioned that, at about the same time, observations were also made at Paris by Marie Davy and Martin; but they are generally looked upon merely as corroborative of Rosse's work, which was more elaborate and extensive. Rosse considered that his results show that the heat from the moon is mainly _obscure, radiated_ heat; the _reflected_ heat, according to him, being much less in amount.

A moment's thought will show that the moon's heat must consist of two portions. First, there will be _reflected solar heat_. The amount and character of this will depend in no way upon the temperature of the moon's surface, but solely upon its reflecting power. And it is to be noted that moon-_light_ is only a part of this reflected radiant energy, differing from the invisible portion of the same merely in having such a wave-length and vibration period as to bring it within the range of perception of the human eye.

The second portion of the heat sent us by the moon is that which she emits on her own account as a warm body--warmed, of course, mainly, if not entirely, by the action of the sun. The amount of _this_ heat will depend upon the temperature of the moon's surface and its radiating power; and the temperature will depend upon a number of things (chiefly heat-absorbing power of the surface, and the nature and density of the lunar atmosphere, as well as the supply of heat received from the sun), being determined by a balance between give and take. So long as more heat is received in a second than is thrown off in the same time, the temperature will rise, and _vice versa_.

It is to be noted, further, that this second component of the moon's thermal radiance must be mainly what is called "obscure" or dark heat, like that from a stove or teakettle, and characterized by the same want of penetrative power. No one knows why at present; but it is a fact that the heat-radiations from bodies at a low temperature--radiations of which the vibrations are relatively slow, and the wave-length great--have no such power of penetrating transparent media as the higher-pitched vibrations which come from incandescent bodies. A great part, therefore, of this contingent of the lunar heat is probably stopped in the upper air, and never reaches the surface of the earth at all.

Now, the thermopile cannot, of course, discriminate directly between the two portions of the lunar heat; but to some extent it does enable us to do so indirectly, since they vary in quite a different way with the moon's age. The simple _reflected_ heat must follow the same law as moonlight, and come to its maximum at full moon. The _radiated_ heat, on the other hand, will reach its maximum when the average temperature of that part of the moon's surface turned toward the earth is highest; and this must be some time after full moon, for the same sort of reasons that make the hottest part of a summer's day come two or three hours after noon.

The conclusion early reached by Lord Rosse was that nearly all the lunar heat belonged to the second category--dark heat _radiated_ from the moon's warmed surface, the _reflected_ portion being comparatively small--and he estimated that the temperature of the hottest parts of the moon's surface must run as high as 500° F.; well up toward the boiling-point of mercury. Since the lunar day is a whole month long, and there are never any clouds in the lunar sky, it is easy to imagine that along toward two or three o'clock in the lunar afternoon (if I may use the expression), the weather gets pretty hot; for when the sun stands in the lunar sky as it does at Boston at two P.M., it has been shining continuously for more than two hundred hours. On the other hand, the coldest parts of the moon's surface, when the sun has only just risen after a night of three hundred and forty hours, must have a temperature more than a hundred degrees below zero.

Lord Rosse's later observations modified his conclusions, to some extent, showing that he had at first underestimated the percentage of simple reflected heat, but without causing him to make any radical change in his ideas as to the maximum heat of the moon's surface.

For some time, however, there has been a growing skepticism among astronomers, relating not so much to the correctness of his measures as to the computations by which he inferred the high percentage of obscure radiated beat compared with the reflected heat, and so deduced the high temperature of lunar noon.

Professor Langley, who is now engaged in investigating the subject, finds himself compelled to believe that the lunar surface never gets even comfortably warm--because it has no blanket. It receives heat, it is true, from the sun, and probably some twenty-five or thirty per cent. more than the earth, since there are no clouds and no air to absorb a large proportion of the incident rays; but, at the same time, there is nothing to retain the heat, and prevent the radiation into space as soon as the surface begins to warm. We have not yet the data to determine exactly how much the temperature of the lunar rocks would have to be raised above the absolute zero (-273° C. or -459° F.) in order that they might throw off into space as much heat in a second as they would get from the sun in a second. But Professor Langley's observations, made on Mount Whitney at an elevation of fifteen thousand feet, when the barometer stood at seventeen inches (indicating that about fifty-seven per cent. of the air was still above him), showed that rocks exposed to the perpendicular rays of the sun were not heated to any such extent as those at the base of the mountain similarly exposed; and the difference was so great as to make it almost certain that a mass of rock not covered by a reasonably dense atmosphere could never attain a temperature of even 200° or 300° F. under solar radiation, however long continued.

It must, in fact, be considered at present extremely doubtful whether any portion of the moon's surface ever reaches a temperature as high as -100°.

The subject, undoubtedly, needs further investigation, and it is now receiving it. Professor Langley is at work upon it with new and specially constructed apparatus, including a "bolometer" so sensitive that, whereas previous experimenters have thought themselves fortunate if they could get deflections of ten or twelve galvanometric divisions to work with, he easily obtains three or four hundred. We have no time or space here to describe Professor Langley's "bolometer;" it must suffice to say that it seems to stand to the thermopile much as that does to the thermometer. There is good reason to believe that its inventor will be able to advance our knowledge of the subject by a long and important step; and it is no breach of confidence to add that so far, although the research is not near completion yet, everything seems to confirm the belief that the radiated heat of the moon, instead of forming the principal part of the heat we get from her, is relatively almost insignificant, and that the lunar surface now never experiences a _thaw_ under any circumstances.

Since the superstition as to the moon's influence upon the wind and weather is so widespread and deep seated, a word on that subject may be in order. In the first place, since the total heat received from the moon, even according to the highest determination (that of Smyth), is not so much as 0.00001 of that received from the sun, and since the only hold the moon has on the earth's weather is through the heat she sends us (I ignore here the utterly insignificant atmospheric _tide_), it follows necessarily that her influence _must_ be very trifling. In the next place, all carefully collated observations show that it _is_ so, and not only trifling, but generally absolutely insensible.

For example, different investigators have examined the question of nocturnal cloudiness at the time of full moon, there being a prevalent belief that the full moon "eats up" light clouds. On comparing thirty or forty years' observations at each of several stations (Greenwich. Paris, etc.), it is found that there is no ground for the belief. And so in almost every case of imagined lunar meteorological influence. As to the coincidence of weather changes with changes of the moon, it is enough to say that the idea is absolutely inconsistent with that progressive movement of the "weather" across the country from west to east, with which the Signal Service has now made us all so familiar.

Princeton, April 12, 1884.

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APPLE TREE BORERS.

The apple tree borers have destroyed thousands of trees in New England, and are likely to destroy thousands more. There are three kinds of borers which assail the apple tree. The round headed or two striped apple tree borer, _Saperda candida_, is a native of this country, infesting the native crabs, thorn bushes, and June berry. It was first described by Thomas Say, in 1824, but was probably widely distributed before that. In his "Insects Injurious to Fruit," Prof. Saunders thus describes the borer:

"In its perfect state it is a very handsome beetle, about three-quarters of an inch long, cylindrical in form, of a pale brown color, with two broad, creamy white stripes running the whole length of its body; the face and under surface are hoary white, the antennæ and legs gray. The females are larger than the males, and have shorter antennæ. The beetle makes its appearance during the months of June and July, usually remaining in concealment during the day, and becoming active at dusk. The eggs are deposited late in June and during July, one in a place, on the bark of the tree, near its base. Within two weeks the young worms are hatched, and at once commence with their sharp mandibles to gnaw their way through the outer bark to the interior. It is generally conceded that the larvæ are three years in reaching maturity. The young ones lie for the first year in the sapwood and the inner bark, excavating flat, shallow cavities, about the size of a silver dollar, which are filled with their sawdust-like castings. The holes by which they enter being small are soon filled up, though not until a few grains of castings have fallen from them. Their presence may, however, often be detected in young trees from the bark becoming dark colored, and sometimes dry and dead enough to crack."

On the approach of winter, it descends to the lower part of its burrow, where it remains inactive until spring. The second season it continues its work in the sapwood, and in case two or three are at work in the same tree may completely girdle it, thus destroying it. The third year it penetrates to the heart of the tree, makes an excavation, and awaits its transformation. The fourth spring it comes forth a perfect beetle, and lays its eggs for another generation.

THE FLAT-HEADED BORER.