heated before brazing as described in speaking of the autogenous welding process.

Simple Methods of Testing Lubricating Oils.-To find if an oil contains certain solid impurities, add kerosene to half a cup of the oil until the mixture becomes quite thin. This thin fluid is now passed through filter paper or ordinary colorless blotting paper. As soon as all of the thinned oil has passed through, the blotting or filter paper is washed with kerosene. The residue that remains, if there is any, will show whether the oil contains any solid impurities. Impurities of this kind may also be determined in a coarse way by smearing a piece of common correspondence or pad paper with the suspected oil and holding it against the light. If the oil is free from solid impurities the blot of oil will be equally transparent everywhere. If not, the solid particles of sediment will be plainly visible.

To test whether an oil becomes resinous or not, it must be poured in a shallow dish, and it is then to be left for about a week in some warm place. If at the end of this period there is not the slightest evidence of a crust you may consider the lubricant to be all right. These oils may also be tested by mixing them with nitric acid. If the oil is pure, a thick mass will form in a few hours. Oils that resinify do not thus clot, but remain very thin.

Among other impurities in oils are to be found injurious acids. When acids occur in lubricating oils they destroy the parts of machines and other apparatus that they lubricate much more quickly than should be the case. A test for such impurities is found in mixing the lubricating oils with copper oxide or copper ash. These are added to the oil in a glass container. When, if the oil is free from acid, it retains its original color. If acids are present their action on the copper makes the color greenish or bluish. This test may also be made by dropping the oil on a sheet of copper or brass. Here it should be left for a week, when at the end of that time if acid is present, a greenish discoloration will be seen on the metal. Almost any of the chemical test for acid as with colored solutions and litmus paper will indicate the occurrence of acid. Litmus paper turns pink in the presence of acid. In its absence a blue. color will be apparent.

To compare the lubricating values of several oils a few drops. must be placed on a smooth, slightly inclined metal or glass sheet. The better and the greasier the oil the farther will a drop of it travel in any given time you determine upon.

Evils of Exhausting in Closed Shop. With the coming of cold weather adjustments to motors are often made in the garage or testing shop proper, instead of outside, as is the case when weather conditions are mild. Many of the garages are insufficiently heated. and of course all doors and windows are kept closed in order to retain what heat there is present. When such is the case, care must be taken that the motors be run very little unless the windows and doors are opened to provide for ventilation. The exhaust gas is very poisonous and cases are known where workmen have narrowly escaped asphyxiation, when running motors continuously in the shop and exhausting directly into the room. If it is necessary to run a motor continuously and conditions are such that windows or doors cannot be opened for ventilation, it will be found desir able to lead the exhaust gas from the room by attaching a piece of heavy rubber hose from the discharge pipe of the muffler to a window, which need be open but a trifle, to allow the end of the rubber hose to hang out into the air. Such a simple precaution will save many a severe sick headache or something more serious. Where the hose goes on the exhaust pipe it must be lined with asbestos, t prevent the heat of the pipe decomposing or burning the hose.. Owing to the free flow provided for the gas, the hose will not be come unduly heated at other parts.

The exhaust gases from a gasoline engine are composed of nitrogen, a little free oxygen, hydrocarbon, hydrogen, carbon monoxide and carbon dioxide, the last two being considered dangerous. The presence of carbon dioxide as a product of combustion of the gasline was recognized as an objection from the beginning of the us of these machines, but attention was called to the fact that the amount produced was relatively small compared to other sources of this gas, and it was not likely to be made in dangerous quantities. The effect of carbon dioxide, except in relatively large per centages, is confined to reducing the oxygen content of the air that is breathed. The presence of carbon monoxide in the exhaust gases

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in injurious quantities was less apparent, but it appears from what is now known that this is the limiting factor in the use of engines exhausting into poorly ventilated places. The presence of carbon monoxide in the air in relatively small quantities has been shown to have a marked effect upon the blood, producing sickness, and if inhaled in sufficient quantity, death. After careful inquiry, the best that can be stated at this time is that without injury to health, no more than 0.1% of carbon monoxide can be breathed and that for a short and infrequent intervals. It is probable that one-half of this percentage could be allowed for a considerable period of time without noticeable effect. The per cent. of carbon monoxide in the garage air depends upon the amount made by the engines running and on the quantity of air with which it is mixed. It will be necessary to provide ventilation for the worst combination of gases which such engines can make under unskillful handling, or else to become informed as to the actual amount of carbon monoxide produced and provide air accordingly.

It is not sufficient to consider the average amount produced as distributed over the whole time of running such a machine. The total quantity of gasoline burned in any one day may have produced but a small quantity of carbon monoxide, but if this has been confined to a relatively short period during bad carburetor adjustment, and in some poorly ventilated space, the momentary percentage may be very high and the consequence may be fatal. It is evident that to be entirely safe the ventilation must be sufficient to keep the percentage of carbon monoxide below the assigned limit. when the engine is producing the maximum quantity possible. If the maximum quantity is provided for by proper ventilation, the chance of injury to health may be considered to be remote. Certain peculiarities of gasoline engines cause the percentage of carbon monoxide generated to vary between rather wide limits, but the maximum is fairly constant. No other constituent of the exhaust gases varies so much or so rapidly with slight changes of adjustment as does the carbon monoxide. Conveying the exhaust gas to the outer air is the simplest and most positive remedy for disposal of this deadly gas.

Instructions for Repairing Storage Battery.—In repairing a

Willard storage battery a definite routine must be followed in tearing down and building up same in order that it will be in the best condition when re-assembled. These steps are as follows:

First: Remove all vent plugs and washers.

Second: Centerpunch both top connectors in each cell which is to be repaired; then drill 3/4-inch into top connector, with a 5inch diameter drill. Now pull off top connector with pair of pliers.

Third: Apply gas flame or blowtorch flame to the top of the battery long enough to soften the sealing compound under the top cover. Now, with heated putty knife, plow out the sealing compound around the edge of top cover.

Fourth Insert a putty knife, or any other thin, broad pointed tool, heated in flame, along underside of top cover, separating it from the sealing compound. Then with putty knife, pry the top cover up the sides and off of the terminal posts.

Fifth: Then, with heated putty knife, remove all sealing compound from inner cover.

Sixth Now play the flame onto the inner cover until it becomes soft and pliable; then take hold of both terminal posts of one cell and remove the elements from the jar, slowly; then lift the inner cover from the terminal posts.

Seventh: Now separate positive and negative elements, by pulling them apart sideways. Destroy old separators.

Eighth To remove a leaky jar, first empty the electrolyte from the jar, and then play the flame on the inside of the jar until the compound surrounding it is soft and plastic; then with the aid of two pairs of pliers, remove it from the crate, slowly, lifting evenly.

Ninth To put in a new jar, in place of the leaky one, heat it thoroughly, in a pail of hot water, and force in gently.

Tenth: In re-assembling the battery, first assemble the positive and negative elements, pushing them together sideways; then tur them on the side and with both hold downs in place, insert new - separators, being very careful to have the grooved side of the separators next to each side of each positive plate. Also be careful to have the separators extend beyond the plates on each side. so there will be no chance of the plates short-circuiting. Now press all separators up against hold downs.

Eleventh Heat up inner cover with flame; then place same on terminal posts; then take hold of both terminal posts and slowly lower the elements into the jar

Twelfth Now, with expansion chamber in place on the inner cover, pour the melted sealing compound on to the inner cover,

Fig. 464.-Diagram Showing Construction of Points to be Reached in Rebuilding or Tearing Down Willard Storage Battery.

until it reaches the level of the hole in the top of the expansion chamber,-i.e. so that when the top cover is replaced, it will squeeze the sealing compound off the top of the expansion chambers.

Thirteenth: Now soften top cover with flame and replace on terminal posts until it rests on top of expansion chamber; then place a weight on top cover until sealing compound cools.