is

only necessary to have a sharp point projecting within the inverted belljar, well insulated and to which one terminal of the generating machine connected. The other is connected to a metal plate upon which the jar stands to represent the earth. The jar may be filled with any smoke such as that produced from tobacco, shavings, turpentine, or what not. But a few turns of the machine will suffice to clear the jar of every particle of smoke. The Voss or Wimshurst machine forms the best electrical generating appliance, since it gives a small current at a very high potential. Instantly the smoke will be observed to assume long streamers which fall on the discharge point, the floor and the sides of the jar.

tricity discharged upon a similar scale might be successful in dispelling fog and he forthwith repeated his experiments, this time charging the bell-jar with watery or acid vapor. The current was switched on and inmediately the particles of. vapor coalesced in precisely the same manner as the dust atoms in the smoke. The whole of the fog within the jar was agitated and in a few seconds was observed to be clearing. During the process he stopped the Wimshurst machine and the failure of the current discharge, caused the particles to assume the form of snow, collecting as in the smoke experiment upon the walls of the jar. If the experiment is repeated on a larger scale with the bell jar represented by a room filled with fog, the result is exactly the same as in the first case.

The success of this experiment suggested to Sir Oliver Lodge that elec

The result of these successes in the laboratory prompted its application upon a more extensive practical scale. Unfortunately at that time such a possibility was out of the question, as there were no means of securing the powerful current of electricity required. Though the Wimshurst machine is eminently adapted to the work for laboratory experiments it is far too delicate and too sensitive to moisture to be used out of doors. What was required was a continuous current dynamo capable of working at the high electrical pressure necessary which at

that time had not been produced.

As a consequence the development was perforcedly brought to

standing the very high pressure that would be imposed. The type of rectifier he evolved is shown in the accompanying illustration and when a battery of twelve of these are built and connected up they will rectify a current of a million volts pressure which is the potential required. They will resist this enormous potential

a temporary cessation ready to be continued directly electrical research provided a means of generating the necessary current. Happily this was not long forthcoming. The perfection of Mr. Cooper Hewitt's mercury vapor rectifier provided the missing link. It was soon found capable of working at very high potentials, and by its means alternating current dynamos and transformers could be used so as to ensure the maintained discharge of the current continuously in one direction. only.

Sir Oliver Lodge thereupon resumed his investigations and experiments and in a short time patented a system which is essentially applicable to practical to practical working upon a large scale. He first set to work devising a special form of Cooper Hewitt's rectifier to meet his requirements so as to be capable of with

without conveying

the current in one direction, but in the other they will transmit it quite easily. If a still higher pressure than the above is demanded, it can easily be fulfilled by increasing the number of tubes in the battery. The current can be furnished either from a direct or alternating current dynamo and is transformed up to the pressure required, before being passed to the rectifiers, the positive and negative wires being carried from the latter to the discharging points.

But there is one essential feature in connection with the invention which is vital to its success. The electrical discharge must take place in the freest possible manner, otherwise an undue strain is imposed upon the rectifiers and the insulation. The last-named factor is also highly important. Throughout it must be as perfect as manufacture can make it. The wires themselves which form the conductors from the rectifiers to the discharge points are enveloped in thick gutta percha. Care must be observed that no sharp kinks are produced otherwise the electricity is likely to fly off from such points. Again where it is necessary to suspend the wires of discharge, or to conduct the supply cables

through walls or other obstacles special insulators must be used, in order to overcome all possibilities of leakage, since all surfaces through which such a wire is passed are likely to become electrified to a certain extent, and thereupon form

magnet for attracting particles of moisture and dirt, which adhering thereto, constitute an excellent medium for conducting the electricity. To meet these difficult requisitions Dr. Lodge has devised a special type of insulator which is of elaborate construction and completely fulfills all demands essential to avoid the above mentioned possibilities.

The discharge wire itself is a bare conductor provided at frequent intervals with small knots of sharp points similar to those in a barbed wire fence, and is strung between these insulators. The apparatus can be set up in two ways. Either a single barbed wire from a mast to which one pole is connected and the other is taken to earth, or two wires suspended parallel to one another, positive electricity being discharged from one string of wire and negative from the other.

The latter is a suitable means for

SPECIAL TYPE OF AERIAL INSULATOR. The barbed points of the discharge wire show above the insulator.

BATTERY OF RECTIFIERS,

Used in Lodge's apparatus to secure maximum electrical effect.

clearing waterways, railroad tracks, etc. The barbed wires, one on each side, would be suspended parallel to the river or street, and at a safe height from the ground. In his early experiments with the invention Sir Oliver Lodge stretched wires across the space separating the roof of his laboratory from neighboring buildings, and although the situation was one in which dense fogs are extremely rare, highly valuable experience concerning the utility of the system was obtained.

Following up these conclusive tests a practical demonstration was carried out near Liverpool on the River Mersey, where fogs are not only very prevalent during the season, but are a serious handicap to the commerce of the port, inasmuch as at such periods shipping is either stopped or heavily disorganized. Here a tall mast was erected with a wire attached. Under the influence of the electrical current thrown into the atmosphere, the air within a radius of fifty feet around the discharge point was observed to be quickly cleared, the moisture coalescing into small flakes of snow.

The fact that the apparatus can be installed at small cost and the electrical energy required can be drawn from the ordinary electric supply mains laid in the streets, its commercial application should offer no serious obstacles. Railroads, shipping interests, and various other industries annually lose heavy sums through dislocation of the traffic, causing in the case of the transport companies, heavy congestion at the stations. It would be a simple matter to equip the latter with a complete installation which would have the effect of keeping the area thereof completely clear, even during these periods of the densest fog.

Efforts are being made to submit the invention to a trial in the English metropolis. As is well known the "London particular" has become a tradition of the city, and its character and denseness to which thousands of chimneys belching heavy smoke into the air from

bituminous coal fires contribute very materially, should impose a supreme test upon the invention. It has been decided to erect the experimental installation on the banks of the Thames in Westminster. Apprehensions have been raised that the discharge of such an enormous amount of electricity of such high potential into the atmosphere might exercise highly injurious effects upon telephonic and telegraphic communication, but upon this point it would appear that such interference would be more imaginary than real. However, the trials are being anticipated with great interest by those who suffer so seriously from the commercial point of view from fog visitations, and their success will undoubtedly result in the widespread adoption of the system, more especially when it is practically demonstrated that the cost of dispelling the fog is less than the losses incurred therefrom. This is yet to be shown.

-SHAKESPEARE.

AD, indeed, was the day for the desert farmer, when the fact was brought home to him. by the hard-headed horticulturists of the West that the muchadvertised spineless cactus is worthless as food for man or beast, and still more worthless as a source of sugar or alcohol. Many hopes had been reared on the spineless cactus, that product of Mexico which Nature developed long before the "plant-breeders" came along, and when its failure was certain, some of the men who had dared the desert to win homes and fer

tile fields from its barren wastes began to look about for something to take the place of the defenseless cactus.

Now comes the news from Sinaloa, that state of Mexico which is a twin sister to the desert section of Arizona, California, Southern Nevada and New Mexico, that there is a plant, a fiberproducer, which is immensely profitable, and, at the same time, seems likely to prove suitable to the greater part of the Southwestern desert of the United States. If it prove so, the greatness of the discovery will be second to none in the annals of agriculture in the New World.

No "American" name has as yet been