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ing stones have been the subject of care- cient to cover 82,000 square yards, or ful inquiry and experiment, and the size say 2,343 yards per cart load. I do not finally adopted has a surface of 64 inches consider the hose system suitable for by 4 inches, and a depth of 64 inches. On adoption here, except in the case of steep gradients larger stones are used. steep gradients like High Street and the Formerly the size was 9 inches each way. Bull Ring, where a horse would work These stones were found to get rounded with difficulty. Since 1873 the house at the edges and corners, and to present refuse has had to be placed each an uneven surface. The steam rolling of night in convenient boxes, in front of the macadamised streets is done by con- the houses, the contractor's carts calling tract, the cost being but little less than for and removing the same early in the horse rolling. The asphalte carriage morning. The removal of this house ways are bedded on beton 4 inches thick, refuse costs the city £80,000 per annum; well pressed down (in very wet weather formerly it was a source of income to bitumen is used instead, as the beton the amount of £20,000 per annum. Two does not set quickly), over the beton a causes are alleged for the change: (1) layer of mortar, and then, at the end of deterioration in the value of the refuse, five days a layer of asphalt 14 inch thick. owing to the diminished use of wood as The annual cost of footpaths of all kinds fuel, and increased use of coal and coke within the city is £43,600. The cleansing for houses and factories, and (2) inand flushing of streets and removal of creased distance of farms from the city, house refuse costs annually £160,000. owing to the increase of suburban villas. Each ward has its own set of sweepers,

Trees in Streets and Squares.-Of &c. Since 1873 a special tax has been these there are now about 90,000, besides levied for sweeping footpaths; previous- 20,000 in the cemeteries. The roots of the ly each householder had to do that duty. trees planted in the streets and squares There are in all 3,120 men and women have a network of small drains for the employed in sweeping the streets and supply of moisture.

These are removing refuse. The street watering nected by a central drain, having a valve, on paved streets is done from April 15 and leading to the main sewer. The to September 30; on others from March average cost of a tree, including trans15 to October 15. About 22 per cent. of planting, propping, draining, grid, &c., the area of the streets is watered by is £7, and about 90 per cent. of the jointed pipes, and the rest by watering transplanted trees succeed. There are carts. The first mode is stated to cost three nurseries for trees, with an area of only about half as much, area for area, 6 acres. The qualities sought in such as the second mode, but then the amount trees are (a) rapid growth, (() shade, (c) paid for horse hire is nearly double that non-liability to attack by insects; and in Birmingham. The watering carts be- the trees selected on these grounds are long to the municipality; the horses be- chestnut, elm, the western plane, lime, long to contractors. The hydrants used and maple. 115 men are employed atfor street watering are about 40 yards tending to the trees. The seats in streets apart; the jointed pipes by which the and squares number 300. water is distributed are 1 inch in diame Sewage.—We visited the great sewer ter, in seven lengths of 8 feet each, on in the Rue de la Pépinière, being met wheels, the joints being made with gut- there by the officers of the municipality, ta-percha, the man with his finger on the detailed by order of M. Bufflers. This nozzle regulating the quantity of water sewer was lighted up by means of fiftyput on. We found in the Rue Castigli- six moderator lamps. The man in at one, the carriageway whereof is 224 tendance showed the apparatus for pushyards wide, that it took the man, on an ing along sand and mud deposited on average, thirteen minutes to water only the bottom of the sewer.

The sewer 33 yards in length of carriageway, and first inspected was of the second class. as each length is watered he uses a broom The water pipes and gas pipes are atto sweep up the horse dung, &c. With tached to the crown or sides of the sewone of our horses and carts a man can ers, thus avoiding tearing up the roadput on thirty-five loads, of 330 gallons way when pipes need repairing. A each per day, and this quantity is sutti. truck, with paddle board moved by the

Yol XXIV.-No. 4—21.

We saw

sewer.

current, is used to force along the sand plain has increased on an average 450 and mud. We next visited the main per cent., and in one case 4,000 per cent., sewer, or collector of all sewage coming or a forty-fold increase. The plain confrom the right bank of the Seine, The tains 3,000 acres, of which 1,075 are mean velocity in the collector was 165 treated with sewage. The main pipes feet per minute. The sewers receive (1) are of beton, varying from 2 ft. to 4 ft. large portions of street sweepings; (2) diameter; the smaller are of Doulton's storm water; (3) water thrown out from glazed earthenware. Nine miles further houses; (4) contents of water closets; from the city is a suitable tract of land, (5) urine from closets fitted with double near St. Germains, with an area of 3,750 cylinder. From 500 to 600 men are em- acres, and the city is in treaty with the ployed in the sewers, of whom 32 work State for its permanent acquisition. If in the great collector. The length of successful, it is intended to turn all the this main sewer is 7 miles, the length sewage on to these two plains. of main on the left bank of river is 5 on the sewage farm all kinds of flowers, miles, and the total length of sewers in fruit, vegetables and trees suitable to the city is 500 miles. The daily outfall the climate; the crops ap) healthy of all sewers is 300,000 cubic meters, or and abundant; the water that had passed 66,000,000 gallons.

through the soil seemed quite clean, and Cesspools.Of these there are still in was tasteless. The drain pipes for Paris about 240,000. In the new dis- collecting this filtered water are 6,600 ft. tricts the double cylinder is used; the in length, the upper half, 3,300 ft., havinner cylinder is pierced with holes to ing holes; the lower part next the outfall allow of the escape of liquid matter into being quite closed. The results of exper. the outer cylinder, and thence to the iment so far, in yield, per acre, are : Arti

The solid matter is carried away chokes, 20,000 to 30,000 heads; califlowin closed carts and dried at Bondy, and ers, 12,000 heads, weighing 16 tons; carsold for manure. It retains but one- rots, 32 to 52 tons; celery, over 40 tons; eighth of the nitrogenous elements, and cabbage, 56 tons; onions, 24 to 32 is of little value as manure. The com- tons; potatoes, 12 to 16 tons; pumppany

that undertakes this work receives kins, 48 to 56 tons. About 10,000 a yearly grant in aid.

cabbages are planted to the acre, and of Sewage Farms at Gennevilliers. these about two-thirds succeed. More We visited the works at Asnieres, five than a million heads of cabbages are miles below the city, being met by MM. taken from the plain every year, each Bufflers and Durand-Claye. A centrifu- weighing on the average 11 lbs., or in all gal pump, worked by a 400 horse-power nearly 5,000 tons. It was stated that Corliss engine, lifts in a day about there was no bad taste or smell in the 13,200,000 gallons of sewage (one-fifth plants so long as only the roots were in of the total amount) to a height of 39 contact with the sewage, and that the feet, into pipes which carry it across the plants best suited to sewage treatment Seine to the formerly arid chalky plain are green succulent ones. Young trees of Gennevilliers (a distance of about thrive remarkably well. The experiment 6,600 feet) for distribution by means of has shown that trees well nourished when open channels over the fields and gar- young thrive best ultimately, even if redens. The tube is 3 ft. 7 in. in diame- moved to a poorer soil. To trees the ter. The supply ceases when desired by sewage supply must be stopped at the the farmers. Besides this amount there end of the summer. Mint and other are about 8,500,000 gallons daily received plants, are cultivated for perfumes and on another part of this plain from St. for flavoring, and succeed remarkably Quen, from which it flows without pump- well. Experiments extended over nine ing. The remainder of the city sewage years show that on such soil as the plain is thrown direct into the Seine, causing of Gennevilliers, about 3,960,000 per a horrible stench for miles. The present acre per annum is the quantity that can pumping works have cost £120,000; the be most effectively utilized. At this rate proposed further expenditure is £400,000. about 5,500 acres would suffice for the These works have been seven years in sewage of the city with its 2,000,000 of operation; the value of the land on the people. The sewage is now given gratis,

to prevent abuses. na Commissioner at

but it is proposed to make a small charge the sewage should be by open furrows, as

Gennevilliers. (3) That the supply Inquiry has just reported, and its conclu should be intermittent and frequent. (4) sions may be summarized: (1) Green That sewage be not allowed to touch any plants, cabbage, celery, lettuce, root part of the plant except the root. (5) crops, and “industrial plants," such as That the place of the furrows should be mint, are those best adapted to sewage frequently changed. treatment. (2) That the distribution of

THE RELATION BETWEEN ELECTRICITY AND LIGHT.*

From"

Nature."

Ever since the subject on, which I must be, we don't know. Well, but this have the honor to speak to you to-night need not, necessarily, be depressing. If has arranged, I have been astonished at the same question were asked about matmy own audacity in proposing to deal ter, or about energy, we should have in the course of sixty minutes with a likewise to reply, no one knows. subject so gigantic and so profound, that But then the term matter is a very a course of sixty lectures would be quite general one, and so is the term energy. inadequate for its thorough and exhaust- They are heads, in fact, under which we ive treatment.

classify more special phenomena. I must, indeed, confine myself care Thus, if we were asked what is sulfully to some few of the typical and phur, or what is selenium, we should at most salient points in the relation be- least be able to reply, a form of matter; tween electricity and light, and I must and then proceed to describe its propereconomize time by plunging at once into ties, i. e., how it affected our bodies and the middle of the matter without further other bodies. preliminaries.

Again, to the question, what is heat ? Now, when a person is setting off to we can reply, a form of energy; and discuss the relation between electricity proceed to describe the peculiarities and light, it is very natural and very which distinguish it from other forms of proper to pull him up short with the two energy. questions: What do you mean by elec But to the question, what is electricitricity? and, What do you mean by light? ty? we have no answer pat like this. These two questions I intend to try We cannot assert that it is a form of briefly to answer. And here let me ob- matter, neither can we deny it; on the serve that in answering these fundament- other hand we certainly cannot assert al questions I do not necessarily assume that it is a form of energy, and I should a fundamental ignorance on your part of be disposed to deny it; it may be that these two agents, but rather the con- electricity is an entity per se, just as mattrary; and must beg you to remember ter is an entity per se. that if I repeat well-known and simple Nevertheless, I can tell you what I experiments before you, it is for the pur- mean by electricity by appealing to its pose of directing attention to their real known behavior. meaning and significance, not to their Here is a battery, that is, an electriciobvious and superficial characteristics; ty' pump; it will drive electricity along. in the same way that I might repeat the Prof. Ayrton is going, I am afraid, to exceedingly familiar experiment of drop- tell you, on the 20th of January next, ping a stone to the earth if we were go. that it produces electricity; but if he does, ing to define what we meant by gravita- I hope you will remember that that is tion.

exactly what neither it nor anything else Now, then, we will ask first, what can do. It is as impossible to generate is electricity and the simple answer electricity in the sense I am trying to

give the word, as it is to produce mat* A lecture by Dr. O. J. Lodge, delivered at the London Institution, on December 16, 1880.

Of course I need hardly say that

ter.

What do you

Prof. Aryton knows this perfectly well; phragms. The water cannot move withit is merely a question of words, i. e., of out straining and bending these diawhat you understand by the word elec- phragms, and if you allow it, these tricity.

strained partitions will recover themI want you, then, to regard this bat- selves and drive the water back again. tery and all electrical machines and bat- [Here was explained the process of teries as kinds of electricity pumps, charging a Leyden jar.] The essential which drive the electricity along through thing to remember is that we may have the wire very much as a water pump can electrical energy in two forms, the static drive water along pipes. While this is and the kinetic; and it is, therefore, also going on the wire manifests a whole possible to have the rapid alternation series of properties, which are called the from one of these forms to the other, properties of the current.

called vibration. [Here were shown an ignited platinum Now we will pass to the second queswire, the electric arc between to carbons, tion:

mean by light? an electric machine spark, an induction And the first and obvious answer is, coil spark, and a vacuum tube glow. Also everybody knows. And everybody that a large nail was magnetized by being is not blind does know to a certain exwrapped in the current, and two helices tent. We have a special sense-organ for were suspended and seen to direct and appreciating light, whereas we have none attract each other.]

for electricity. Nevertheless, we must To make a magnet, then, we only need admit that we really know very little a current of electricity flowing round about the intimate nature of light-very and round in a whirl. A vortex or little more than about electricity. But whirlpool of electricity is, in fact, a we do know this, that light is a form of magnet; and vice versa. And these energy; and, morever, that it is energy whirls have the power of directing and rapidly alternating between the static attracting other previously existing and the kinetic forms—that it is, in fact, whirls according to certain laws, called a special kind of energy of vibration. the laws of magnetism. And, moreover, We are absolutely certain that light is a they have the power of exciting fresh periodic disturbance in some medium, whirls in neighboring conductors, and of periodic both in space and time; that is repelling them according to the laws of to say, the same appearances regularly diamagnetism. The theory of the actions recur at certain equal intervals of disis known; though the nature of the tance at the same time, and also present whirls, as of the simple stream of elec- themselves at equal intervals of time at tricity, is at present unknown.

the same place; that in fact it belongs [Here was shown a large electro-mag- to the class of motions called by mathenet and an induction-coil vacuum dis- maticians undulatory or wave motions. charge spinning round and round when The wave motion in this model (Powell's placed in its field.]

wave apparatus) results from the simple So much for what happens when elec- up-and-down motion popularly associated tricity is made to travel along conduct- with the term wave. But when a mathors, i. e., when it travels along like a ematician calls a thing a wave he means stream of water in a pipe, or spins round that the disturbance is represented by a and round like a whirlpool.

certain general type of formula, not that But there is another set of phenomena, it is an up-and-down motion, or that it usually regarded as distinct, and of looks at all like those things on the top another order, but which are not so dis- of the sea. The motion of the surface tinct as they appear, which manifest of the sea falls within that formula, and themselves when you join the pump to a hence is a special variety of wave mopiece of glass or any non-conductor, and tion, and the term wave has acquired in try to force the electricity through that. popular use this signification and nothing You succeed in driving some through, else. So that when one speaks ordinaribut the fow is no longer like that of ly of a wave or undulatory motion one water in an open pipe, it is as if the immediately thinks of something heavpipe were completely obstructed by a ing up and down, or even perhaps of number of elastic partitions or dia- something breaking on the shore. But

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when we assert that the form of energy he was engaged in researches that no called light is undulatory, we by no other man can hope as yet adequately to means intend to assert that anything grasp and follow out: but, fortunately, whatever is moving up and down, or did not occur till he had published his that the motion, if we could see it, book on “Electricity and Magnetism," would be anything at all like what we one of those immortal productions which are accustomed to in the ocean. The exalt one's idea of the mind of man, kind of motion is unknown; we are not and which has been mentioned by comeven sure that there is anything like mo- petent critics in the same breath has the tion in the ordinary sense of the words Principia” itself. at all.

But it is not perfect like the “PrinNow, how much connection between cipia;” much of it is rough hewn, and electricity and light have we perceived requires to be thoroughly worked out. in this glance into their natures? Not It contains numerous misprints and ermuch, truly. It amounts to about this: rata, and part of the second volume is That on the one hand electrical energy so difficult as to be almost unintelligible. may exist in either of two forms—the Some, in fact, consist of notes written static form, when insulators are electri. for private use, and not intended for cally strained by having had electricity publication. It seems next to impossidriven partially through them (as in the ble now to mature a work silently for Leyden jar), which strain is a form of en- twenty or thirty years, as was done by ergy because of the tendency to discharge Newton two and a half centuries ago. and do work; and the kinetic form, But a second edition was preparing, and where electricity is moving bodily along much might have been improveü in form through conductors or whirling round if life had been spared to the illustrious and round inside them, which motion of author. electricity is a form of energy, because The main proof of the electro magthe conductors and whirls can attract or netic theory of light is this. The rate repel each other and thereby do work. at which light travels has been meas

And, on the other hand, that light is ured many times, and is pretty well the rapid alternation of energy from one known. The rate at which an electroof these forms to the other—the static magnetic wave disturbance would travel form where the medium is strained, to if such could be generated (and Mr. the kinetic form when it moves. It is Fitzgerald of Dublin thinks he has just conceivable, then, that the static form proved that it cannot be generated diof the energy of light is electro-static, rectly by any known electrical means) that is, that the medium is electrically can be also determined by calculation strained, and that the kinetic form of from electrical measurements. The two the energy of light is electro-kinetic, that velocities agree exactly. This is the is, that the motion is not ordinary mo- great physical constant known as the tion, but electrical motion-in fact that ratio V, which so many physicists have light is an electrical vibration, not a ma- been measuring, and are likely to be terial one.

measuring for some time to come. On November 5th, last

year,

there Many and brilliant as were Maxwell's died at Cambridge a man in the full discoveries, not only in electricity, but vigor of his faculties—such faculties as also in the theory of the nature of gases, do not appear many times in a century and in molecular science generally, I can

- whose chief work has been the estab. not help thinking that if one of them lishment of this very fact, the discovery is more striking and more full of future of the link connecting light and elec- significance than the rest, it is the one I tricity; and the proof-for I believe it have just mentioned—the theory that amounts to a proof—that they are differ- light is an electrical phenomenon. ent manifestations of one and the same The first glimpse of this splendid genclass of phenomena—that light is, in eralization was caught in 1845, five-andfact, an electro-magnetic disturbance. thirty years ago, by that prince of pure The premature death of James Clerk experimentalists, Michael Faraday. His Maxwell is a loss to science, which ap- reasons for suspecting some connection pears at present, utterly irreparable, for between electricity and light are not

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