May 24, 1889.] 



SCIENCE. 



393 



ture, the high speed of the cars (going much faster than the cables), 

 the easy motion of the car, the freedom from jerking and lack of 

 dinger elements, fully attest the wisdom displayed. 



The cars as now equipped are able to tow additional cars, their 

 equipment being of sufficient power. They have fully demon- 

 strated their efficiency in many instances ; in one case having 

 pushed the Avondale cars up the 75-per-cent May Street grade 

 when the horses were stalled from overloading, and in another 

 pushing the heavy cable-trains back upon the track at a recent 

 occurrence. 



The performance of regular commercial service by these Daft 

 motor cars over a road upon which there are not over six hundred 

 feet of straightaway track (in one mile there being six cross-overs, 

 eight curves, and grades as high as 7+ per cent, travelling for a por- 

 tion of the road over a regular cable-line), and the ease with which 

 they are able to run away from the cable-cars, mounting grades 

 continuously vvet by street-sprinkling carts, demonstrate that the 

 Daft system in Cincinnati has scored a complete success, and 

 justifies the confidence reposed in it by the managers of the street- 

 railway company. 



Praises for the manner of its construction, its equipment, and its 

 operation, are heard everywhere. One of the most remarkable 

 features about this line is the double underneath contact trolley. 

 It requires no attention from driver or conductor: in fact, were it 

 not for the ordinances requiring a conductor to each car, his ser- 

 vices would be wholly unnecessary. The trolley moves with the 

 same ease as the car upon the track, and its liability to leave the 

 wires is very much less. Its construction is such that it regulates 

 itself to all the various dips, angles, curves, etc., with the greatest 

 facility. 



Another important feature of the Daft system is its great econ- 

 omy. 



The power is taken from the engine which drives the Gilbert 

 Avenue cable, and so some fluctuation of speed in the generator 

 results, but not sufficient to interfere in any way with the success- 

 ful operation of the electric road. 



Half-hourly records are kept of voltmeter and ammeter read- 

 ings, the dynamo speed, and the temperature of the engine-room. 

 From these it can readily be seen when the car is ascending grades, 

 when descending, when at grade, when with more than an ordinary 

 load, etc. At the dynamo station it is practicable to tell at any 

 hour of the day the relative position of the cars to the line. Power 

 is only absorbed by the motors upon the car to meet the require- 

 ments made upon it by their several loads. Of course, under such 

 circumstances, when there is no demand for power, there can be 

 no expenditure, and the result is the highest economy. It is usual 

 with street-railway people to base the success of any system, 

 whether it be by horses, by cable, or by electricity, upon the dollar- 

 and-cents basis. In this respect the Daft system recommends itself 

 to thoughtful business-men. 



INSECTICIDES AND THEIR APPLICATION. 



As the season of the annual warfare between vegetable life and 

 its insect enemies has come round once more, our readers will 

 probably find interesting a report on insecticides recently published 

 iDy the Ohio Agricultural Experiment Station. The director of the 

 station states that insecticides, or the substances used for destroy- 

 ing insects, may broadly be divided into two classes : (i) internal 

 poisons, or those which take effect by being eaten along with the 

 ordinary food of the insect ; and (2) external irritants, or those 

 which act from the outside, closing the breathing-pores, or causing 

 death by irritation of the skin. Besides these, however, various 

 other substances are used in preventing insect-attack, keeping the 

 pests away because of offensive odors, or acting simply as mechani- 

 cal barriers. 



The most important insecticides are the poisons. Of these the 

 most popular are the various combinations of arsenic, known as 

 "Paris green," " London purple," "slug-shot," and a large num- 

 ber of patent insecticides sold under various names. 



Paris green is a chemical combination of arsenic and copper, 

 called arseniate of copper. It contains about fifty-five or sixty per 

 cent of arsenic, and retails at about thirty cents per pound. It is 



practically insoluble in water, and may be applied either dry or 

 wet. In the former case it should be well mixed with some fine 

 powder as a diluent : plaster, air-slacked lime, flour, road-dust, and 

 finely sifted wood-ashes, all answer the purpose fairly well, though 

 lime or plaster is usually preferable. The proportion of poison to 

 diluent varies greatly with different users : one part poison, to 

 fifty, and even one hundred, of diluent, will usually be effective, if the 

 mixing be thoroughly done. In the wet mixture for fruit and shade 

 trees, use one pound poison to 150 gallons water, and keep well 

 stirred. The chief objection to Paris green is that it is so heavy 

 that it settles quickly to the bottom of the vessel, — very much 

 more quickly than London purple. It is also more expensive. 



London purple is a by-product in the manufacture of aniline dyes, 

 produced by Hemingway's London Purple Company of London, 

 England. It contains nearly the same percentage of arsenic as 

 Paris green, and is much cheaper, retailing at about fifteen cents 

 per pound. It is a finer powder than the green, and consequently 

 remains in suspension much longer. It may be used in the same 

 way, — as a powder or in water, — and the proportions given above 

 answer very well for it. 



White arsenic is sometimes recommended as an insecticide, but 

 fortunately is rarely used. It is much more dangerous to have 

 around than either of the above highly colored compounds, and in 

 practice is very liable to burn the foliage to which it is applied. 



The principal substances used for killing insects, by contact, are 

 the following : — 



Hellebore is a powder made of the roots of a plant called white 

 hellebore ( J'eratriim album). It is a vegetable poison, but much 

 less dangerous than the mineral arsenical poison, and kills both by 

 contact and by being eaten. It may be applied as a dry powder 

 or in water (an ounce to three gallons). It retails at about twenty- 

 five cents per pound, and is especially excellent for destroying the 

 imported currant-worm. 



Pyrethrum is an insecticide of recent introduction, made from 

 the powdered flowers of plants of the genus Pyrethrum. There 

 are three principal brands upon the market, known as " Persian in- 

 sect-powder," " Dalmatian insect-powder," and " buhach," the last 

 being a California product. The greatest obstacle to the use of 

 pyrethrum has been the difficulty of obtaining the pure, fresh arti- 

 cle. If exposed to the air, the poisonous principle volatilizes, and 

 the powder is worthless : hence dealers should purchase a fresh 

 supply each season, and should keep it in air-tight vessels. Pyre- 

 thrum is used mainly either as a dry powder or in water (one ounce 

 to three gallons), but may also be used in the form of a tea or a 

 decoction, a fume, or an alcoholic extract diluted. For use as a 

 dry powder, it may advantageously be diluted with six or eight 

 parts of flour. It is especially excellent for clearing rooms of flies 

 and mosquitoes, and for killing the common cabbage-worms. It 

 is practically harmless to man and the higher animals. 



Kerosene emulsion is made by adding two parts of kerosene to 

 one part of a solution made by dissolving half a pound of hard 

 soap in one gallon of boiling water, and churning the mixture 

 through a force-pump with a rather small nozzle until the whole 

 forms a creamy mass, which will thicken into a jelly-like substance 

 on cooling. The soap solution should be hot when the kerosene is 

 added, but of course must not be near a fire. The emulsion thus 

 made is to be diluted, before using, with nine parts cold water. 

 This substance destroys a large number of insects, such as the 

 chinch-bug, cabbage-worm, and white grub, and is a comparatively 

 cheap and effective insecticide. Besides its use as an emulsion, 

 kerosene alone is frequently used for various pests. It is espe- 

 cially valuable in destroying vermin on domestic animals and in 

 hen-houses. 



Carbolic acid, especially in its crude state, is valuable for various 

 insecticidal purposes. An excellent wash for preventing the inju- 

 ries of several tree-borers is made by mixing one quart soft soap, 

 or about a pound of hard soap, with two gallons water, heating to 

 boiling, and then adding a pint of crude carbolic acid. Carbolic- 

 acid soaps are largely used for destroying vermin on domestic ani- 

 mals. 



Tobacco is a very valuable insecticide for use against vermin on 

 domestic animals and green-house pests. It may be used in the 

 form of a decoction, a smoke, or dry. The refuse stems from the 



