페이지 이미지
PDF
ePub

ported entirely within the tube and free wire in the previous experiment, and to rotate, by a similar cup (surmounting passing the current, rotation occurred, a fixed vertical brass rod) at the lower showing that the chief use at least of the end of the tube, the upper end of the coil current was to impart longitudinal axial wire being kept in position by a magnetism to the axial wire, and that vertical brass rod fixed above the coil, the rotation was not simply due to any and terminated at its lower end by a reaction between the coil and that wire. sharp point of platinum in the mercury Reversing the direction of the current сир. .

did not reverse the direction of rotation. A current from 6 one-pint Grove's ele- In another experiment similar to this, I ments arranged as 3 being now passed formed about 12 centims. in length of through the coil, brass rods, and axial the middle part of the axial wire of copwire, the latter rotated rapidly.

per instead of iron, and obtained simiWith a downward current through the lar rotation ; but as copper is only axial wire, and north poles * at the ends slightly capable of acquiring longitudiof the tube, the upper end of the wire nal magnetism from a coil current surrotated in the same direction as the rounding it, a precisely similar apparahands of a watch. Reversing the direc- tus having an axial wire composed ention of the current either in the coil or tirely of that metal would not rotate. irou rod, reversed of course the direction These experiments and the following of motion. The rotation in this case ones produce a striking effect in a lecwas not due to obliquity of coil-current, ture, because the rotation appears to be because that was neutralized by the sec- produced without reaction of the moving ond layer of coils ; nor to portions of part of the apparatus upon any external transverse currents proceeding to or or fixed body. from the brass rods, because each of To determine whether the longitudithose portions was 10 centims. distant nal element of the coil current obtained from the ends of the axial wire ; nor was by obliquity of winding of the wire it due to the portions of current entering might be substituted for the longitudior leaving the coil, because they entered nal current through the magnet, I took and left at the same part and in parallel an iron wire 13 centims. long and 1.7 directions, and thus neutralized each millim. diameter, sharp-pointed at its other's effect. A copper wire substituted lower end, soldered near to that end one for the iron one would not rotate, proba- extremity of a cotton covered copper bly because copper is so little capable wire 1.7 millim. in diameter, coiled the of acquiring longitudinal magnetism. latter in one direction to the middle part

To ascertain if the rotation was merely of the iron wire, then reversed the direcdue to an action of the current in the tion of winding and coiled to the other coil upon either the axial current or lon- end of the iron, and terminated the coil gitudinal magnetism of the iron, or by a little brass cup just above the upper whether the coil current simply per- end of the iron wire as before. By supformed the function of longitudinally porting this apparatus as in the previous magnetizing the axial wire, I took an experiments, and passing the current, iron wire 23 centims. long and 2.7 mil. rapid rotation took place, proving that lims. diameter, sharp pointed at its lower longitudinal current in the iron itself end, soldered to its upper end a double was not necessary. wire of cotton-covered copper, each wire

To ascertain whether the longitudinal being 1.7 millim. diameter, coiled the element of the current was essential to double wire upon the axial rod in two the motion, I constructed a similar aplayers (so as to enable two similar poles paratus to the last, but instead of attachto be formed at the extremities of the ing the upper end of the coil wire direct axis), and terminated the copper wires to the brass cup, I continued the copper by a little brass mercury cup just above wire vertically downwards to the bottom the top end of the vertical iron axis. By of the coil, to neutralize the effect of supporting this apparatus as the axial obliquity of winding; then carried it

outwards and upwards in the form of a * By a North pole I mean that which points to the large rectangle 5 centims. distant from

, North.

the coil and on to the mercury cup. On

passing the current rotation occurred right-handed or left-handed ( )*, acfreely, showing that the longitudinal cording to the direction in which its coils current was not essential to the motion. were wound. It follows from this that This experiment, and that described in a current, the direction of which is alparagraph 4, appears to prove that the ternately reversed, will drive the apparotation is not an effect of any obliquity ratus quite as well as one in one uniform or spiral arrangement of the axis of the direction. magnetized iron molecules with regard As the rotation was apparently due to to the axis of the wire, produced by the the influence of the tangential poleless combined action of the transverse and magnetism of the portions of vertical longitudinal elements of the current in current in the fixed conductors upon

the the coil, because the latter element was longitudinal magnetism of the vertical neutralized, but that it is an effect of the iron axis and its coils, I now endeavored tangential poleless magnetism in the to increase the effect. For this purpose fixed wires above and below upon the I substituted for the upper brass rod a longitudinal magnetism of the movable fixed coil consisting of one layer of copiron axis and its coil.

per

wire upon an iron wire axis, but havAs an electric solenoid, however, pos- ing dissimilar poles at its ends and no sesses in some degree many of the prop- poles at its middle part, and placed beerties of a magnet, its longitudinal mag. tween it and the lower brass rod a siminetism, though feeble, must have opera- lar right-handed one to that described ted in some of the previous experi- in paragraph 6 and free to rotate. The ments; and I therefore now tried to opposed poles of the fixed and movable obtain rotation of one by the action of coils were of opposite kinds, i. e. north vertical currents. Upon a very thin and south. On passing a current from wooden tube 15 centims. long and 12 a Noe's thermopile of 96 elements f conmillims. external diameter, I coiled a nected as 24, rapid rotation in a rightsingle stout cotton-covered copper wire handed direction occurred. I now subfrom one end to the other, reversing the stituted for the lower brass rod another direction of winding at the middle of the fixed coil, similar to the upper one, but tube, and surmounting the upper end of of an opposite direction of polarity, and the wire by a small brass cup containing passed the current again ; still more mercury. The lower end of the wire rapid rotation in the same direction took was sharply pointed, and the coil was place, and the effect was very striking. supported as in the previous experiment. In this latter instance two south poles By passing the current from 6 one-pint free to move were opposed to two fixed Grove's elements arranged as 3, faint north poles, and in each instance the cursigns of rotation were observed. rent was passed upwards. In the second

In each of these cases of rotation an experiment also the longitudinal magupward vertical current entering a lower netic influence of each opposed iron axis south pole or leaving an upper one and coil acted upon the tangential magcaused the upper end of the rod to rotate netism of the longitudinal element of in the direction of the hands of a watch, the end of the copper coil current opand a downward current entering or leav- posed to it, and thus both the longitudiing a north pole also produced that nal and the tangential magnetism of direction of motion, and reversing the each of the four opposed ends co-operapoles in either case reversed the effect. ted to produce a most effective result.

In each of these instances of rotation, With a thicker axial wire in the moving without the aid of a current near the coil the rotation was not so rapid ; and middle of the magnet, the coil being so with an axial wire of the usual thickness, constructed that the current in it could but a double layer of copper wire coils, not be reversed without reversing that in and the current passing through the the fixed conductors near it, reversing axial wire, the rapidity of rotation was the direction of the current did not re- not much altered, probably because the verse that of the rotation, because the two acting influences were reversed to-end of which rotates in the same direction as the

* By a "right-handed" coil, I mean one the upper gether; and therefore each apparatus hands of a watch. had its own direction of rotation, either such experiments.

t I have found this apparatus very convenient for

increased weight and friction counter- current from the thermopile produced acted the effect of the increased magnet- very rapid rotation. This result proves ism. By substituting for the right- that the rotations are not due to terres handed movable coil with south poles at trial magnetic influence. its extremities, in these experiments, a As the directions of magnetic polarity, left-handed one with north poles at its electric current, and rotation agree with ends opposed to north poles of the fixed those in the different forms of Ampère's ones, and passing the current, no rota- experiment, and as in most, if not all, of tion occurred : in this case the longi- the previously known cases of rotation tudinal element of the current in the of a bar magnet or conducting wire on movable coil, acting upon the longitudi- its axis an electric current passes through nal magnetism of the fixed iron axis and the end of the bar or wire, it is evident its coil, tended to produce rotation in that those rotations were due, not only one direction, and the longitudinal mag- to the portions of current in the mernetism of the movable axis and its coil, cury and fixed conductors connected acting upon the longitudinal element of with it near the middle of the magnet or the current in the fixed coil, tended to wire, but also to the influence of the curproduce rotation in the opposite direction. rents in the fixed conductors near the

I now substituted for the movable ends of the magnet or wire. coil a vertical wire of iron 13 centims. [NOTE.-It having been suggested by long and 1.7 millim. diameter, sur. Professors Maxwell and Stokes that the mounted by a small brass mercury cup, rotation in the foregoing experiments passed the current from the thermopile, was due to the influence of the portions and obtained rotation, but less rapid of current in the cups of mercury, or in than before, probably because of the less the fixed conductors near the ends of the degree of longitudinal magnetism; but movable wire or magnet upon the movaby enclosing this wire in the axis of a ble magnet, I diminished the internal fixed coil which produced appropriate diameter, both of the upper and lower and similar coils at its two ends, as in cups, from 4 millims. to 1.75 millim., and paragraph 4, and repeating the experi- arranged the following apparatus and ment, very great velocity of rotation was experiment. obtained. Rotation of somewhat The fixed upper wire was of brass, 2.5 thicker wire of nickel was also obtained, millims. diameter and 60 millims. long; both with and without the aid of the it had no coil upon it, and was used as a current in the middle fixed coil. I also conductor only; its lower end terminated tried, without the aid of the middle fixed in a fine point of a steel needle projectcoil and with it, a copper wire of similar ing 6 millims. The lower fixed wire dimensions to the iron one, and obtained (also used as a conductor only) was of rotation freely; in this case the motion platinum, to resist the action of the merwas probably nearly wholly due to the cury; it was 2.3 millims. diameter and action of the longitudinal magnetism of 75 millims. long, with a cavity in its upthe adjacent ends of the fixed axial wires, per end 3.5 millims. deep and 1.75 miland their coils upon the tangential mag- lim. diameter, and containing a thin plate netism produced in the movable copper of ruby in its lower part, with a minute wire by the axial current. Each of these hole in the center for the needle point rotations agreed in direction with those to rotate in. The movable wire was 2.5 of the movable coil.

millims. diameter and 125 millims. long, I also obtained rotation of the iron its upper half being composed of soft wire whilst the wire was in a horizontal iron and its lower half of brass ; its lower position, its ends resting in hollows in end terminated in a needle point like the ends of the iron axis of the two that of the upper fixed wire, and its fixed coils, and the ends of those axis upper end had a cavity and perforated and of the movable wire lying upon the ruby plate like that in the lower fixed surface of pools of mercury in small wire. A voltaic coil 60 millims. long and watch glasses. The movable iron wire 7 millims. internal diameter, composed was enclosed in the axis of a thin iron of four layers of cotton covered with tube within a fixed coil, having appro- stout copper wire, was used to magnetize priate and similar poles at its ends. The the iron half of the movable wire, and

a

fixed by means of a separate support in 3, was passed through the coil and vertia proper vertical position beforehand, so cal wires, and the direction of the poras to enclose in its axis the iron wire tion of the current in the coil alone, also portion only. The little cups were also in the vertical wires alone, was varied ; each half filled with a minute globule of but notwithstanding that plenty of curmercury before putting the movable wire rent passed, no signs of rotation could into its place.

be detected. These results, therefore, After adjusting the wire so as to make strongly support the opinion that the rotation easy, a current from 6 Grove's rotation in the experiments was due to elements of one-pint capacity arranged the action of the portions of the current as a series of 6, also as a double series of in the cups of mercury.]

ON THE ACTION OF COKE SLAG ON FIREPROOF

MATERIALS.

By Dr. B. KOSMANN.

From “Abstracts” of the Institution of Civil Engineers.

A.

B.

THESE experiments were undertaken at the temperature prevailing in the furwith the object of ascertaining what re- nace : lation exists between the composition of the fused slag resulting from the com Silica....

47.91 62.95 bustion of coke at a high temperature

Alumina

30.17 25.23 and the deterioration of the fire bricks

Ferric oxide... 12.16
Ferrous

3.12 subjected to the action of such slag.

Mangapic

0.38 At the same time and for the purpose of Manganous “

0.28 comparison, analyses were made of the Lime..

1.41 0.46 Magnesia.

1.22 ash produced by the same coke when

0.92 Soda..

2.60

2.82 burned at a lower temperature. It has

Potash.

3.34 3.51 been usual, in investigating the action of

Sulphuric acid.

0.82 the slag produced by fuel upon fire-proof Phosphoric

0.55 materials, to analyze the ash of the fuel Metallic iron..

0.09

0.04 before it has undergone fusion. That

Ferrous sulphide.. such a practice must, in many cases, lead

100.01 99.97 to erroneous conclusions may be seen from the examples given below. The The fused slag formed a dark glass of experiments were conducted in regener- the specific gravity 2.52, and enclosing ator furnaces for heating gas retorts. globules of metallic iron. At the higher In these furnaces the fire bricks, espec- temperature, therefore, both iron and ially in the neighborhood of the slits manganese had been reduced to lower through which air is admitted, are very stages of oxidation, part of the former rapidly corroded, unless their composi- even to the metallic state. The sultion is adapted to the acid or basic phates of lime and magnesia had been nature of the slag with which they are either volatalized or removed by mechanbrought into contact.

ical means, and the potash and soda reThe first series of experiments was mained in the slag. Although the ash made with a regenerator furnace on is of a decidedly basic character before Müller and Eichelbrenner's system. fusion, yet the slag produced from it is The coke used was from the Gelsenkirch acid. In this case the use of fire bricks district, and contained 11.92 per cent. of with an excess of acid constituents was ash. When produced at a temperature indicated. Those used contained 89 per which did not suffice to fuse it, the com- cent. of silica, and resisted the action of position of this ash was that given under the fused slag remarkably well. A. B is the ash of the same coke fused In the second series of experiments

A.

B.

A.

B,

[ocr errors]

Loss as gas..

.

the regenerator furnace was constructed phates present. This furnace was lined on Liegel's system. The coke was made with fire bricks containing as high a profrom a mixture of Nettlesworth and portion of alumina as possible; they reLeverson coal. The proportion of ash sisted the action of the basic slag so in the coke was 9.24 per cent. ; its well that their wear was almost imperanalysis is given in the following table ceptible. under A. Arter the furnace had been The coal used in the third series of working for three days the sample B experiments was from Upper Silesia, and was taken. It was but partially fused, contained 3.54 per cent. of ash, of the the action of the furnace being imper- composition given below under A: fect, owing to the air slit being too large. When this had been reduced in size the

Silica..

61.18 61.32 slag was easily fused, and had the com

Alumina.

26.07 23.79 position C:

Ferric oxide..

7.32 Ferrous

7.41 Manganous

0.78 Silica..... 43.34

34.55
{51.80}
Lime.

1.32 3.60 Titanic acid... 0.86

3.40
Magnesia. .

1.18 1.50 Alumina.. 21.16 29.27 41.26

Soda..

0.33 0.80 Ferric oxide 11.84 11.24

Potash

1.79

1,35 Ferrous 0.43

0.47 •Manganic

0.61 1 26 Manganous

0.25

99.66 100.55 Lime...

10.53 6.85 15.14 Magnesia.

0.41 1.12 0.57 Soda.

The regenerator was lined with the best 0.86 0.33 0.06 Potash. 1.88 0.70 0.67

Garnkirk fire bricks; but, as will be seen Sulphuric acid. 7.17

from the analysis B, the slag was of so Phosphoric “ 0.61

acid a nature that these bricks were Sulphur.....

0.19

speedily corroded, and in a short time Metallic iron...

3.75

completely destroyed. Other bricks, 99,27 102.57 100.27 containing 89 per cept. of silica, were

therefore substituted, and left nothing The apparent excess in B is due to the to be desired with regard to durability. oxygen of the iron and manganese com - Journal fur Gasbeleuchtung. pounds, part of which were present in the lower stage of oxidation. The presence of titanic acid is remarkable in these analyses. The changes which took In the early future india-rubber ought place during the first stage of fusion (B) not to be an expensive article. Accordwere not important. In the second ing to information concerning the plant stage (C), when completely fused, the which produces Ceara rubber, contained slag became more basic in its character in the report on india-rubber by Dr. than the ash from which it was derived. H. Trimen, of Ceylon, the plant is very There was a considerable reduction of hardy, and will grow in a dry, rough metallic iron, which was found in numer- soil, and a moderately dry, hot atmosous globules interspersed throughout the phere, while the Para and West India dark, vitreous mass. In this case also rubber plants require a rich alluvial soil, the sulphates had been volatilized. The and a constantly hot-moist atmosphere. iron globules were very impure, contain- Ceara-rubber plants have been found to ing only 36 per cent. of metallic iron. succeed in Ceylon, Calcutta, and Madras,

After the furnace had been in work but the climate of Singapore is too wet some months the draught became defect- for them. It is suggested, says the ive, and, on the flues being opened, Journal of the Society of Arts, that they were found lined with a inch coat- plantations should be formed on ing of a light, porous substance, which hausted coffee land. The tree grows to was found on analysis to contain 72 per about thirty feet or more in height, and cent. of silica and a large proportion of forms a dense rounded crown. It atsulphates. It probably owed its origin tains a diaineter of four inches or five to the decomposition of the slag by inches in about two years, when it may steam, assisted by the action of the sul- be tapped.

ex

« 이전계속 »