as 27 gallons of from 8 to 10 ounce strength. How many pounds of pure ammonia gas, NH,, does this amount of liquor represent?

8. Give a description-illustrated with a sketch of a longitudinal section of both spigot and hub showing outside diameter of spigot, all dimensions of the hub or bell, the shape of the lead groove in the bell, and the depth and finished shape of the lead-of the making of a lead joint in a 4 inch cast iron main. Give also the amount of lead and packing used and the length of time that should be required to do the work.

9.

10.

II.

12.

What is a Holophane globe and how does it affect the useful light given by the source of light over which it is used?

In setting a gas range which has an oven burner and four top burners, what size of pipe should be used, and to what size meters should it be connected? Give the reasons for your answer.

Give a description, illustrated with sketches, of two or more methods of connecting services to street mains, and state what you consider to be the respective advantages and disadvantages of each method.

Describe the preparation and use of cement mortar for brick work construction, with the precautions to be observed to insure strength and uniformity.

(Answers to these questions are due December 1, 1905.

ANSWERS TO FOURTH SERIES OF QUESTIONS SECTION OF 1908-PRACTICAL CLASS-AMERICAN GAS

LIGHT ASSOCIATION,

I. What conditions, other than the size, would determine your choice in selecting one of several kinds of anthracite coal offered for use as the generator fuel in a carburetted water gas apparatus?

Answer. The object in selecting an anthracite coal for use as the generator fuel in a carburetted water gas apparatus is to obtain the coal that will produce the most gas at the smallest cost. The price being equal, the cost of the gas is affected by the quantity of gas that can be made from a given weight of fuel, the amount of sulphur compounds in the gas, the rate at which the gas can be made and the amount of labor required to handle the apparatus. The quantity of gas that can be made depends largely upon the amount of fixed carbon in the coal and also upon the hardness and ability to withstand handling, and the weight of the fuel above it in the generator, without breaking up into small pieces. The amount of sulphur compounds in the gas depends, of course, upon the amount of sulphur in the coal, other things being equal. The rate at which the gas can be made is influenced by the ability of the coal to resist crushing, without which the fire cannot be kept in good condition for gas making as well as by the amount and character of the ash through its influence upon the nature and quantity of the clinker formed. The latter also determines the amount of labor required for cleaning the fire, while the cost of labor for gas making proper depends upon the rate at which the gas is made.

The best coal for the purpose named is therefore the one that contains the largest percentage of fixed carbon and is hard enough not to break up into small pieces in the generator, or while being handled before being put into the generator, and shows only small percentages of sulphur and of an ash that produces a clinker that does not unduly obstruct the passage of the blast and steam through the fire, nor make the cleaning of the fire difficult. To fulfill this condition, the ash should not contain much sulphur or iron. Since a red color is due to the presence of iron, the white ash coals give the least trouble from clinker.

It is, however, difficult to secure a coal that possesses all of the above qualities in the highest degree, and also entirely possible to pay too much for them. Therefore, in making a choice between different kinds of coal it is always necessary to balance advantages in one direction against disadvantages in another and so determine carefully the relative values of the

different samples, selecting the one that is shown in this way to be the cheapest at its price. (Trustees.)

2. How do you determine when the checker bricks in a carburetted water gas apparatus need cleaning?

Ans. The checker bricks of a carburetted water gas apparatus should be removed and cleaned, or renewed when dirty or crushed, or disintegrated. Checker bricks may become covered with a non-conducting coating of ashes or carbon, or both, making impossible the desired exposure of the oil vapors to properly heated brick surfaces. When bricks are coated or saturated with carbon the surface heats rapidly, because the carbon burns, and the gas maker is deceived by the glowing carbon and believes the bricks to be hotter than they are. It is possible to tell something of the condition of the checker bricks by observation through the sight cocks provided for the purpose. Other indications of dirty bricks are a falling off in the rate of make per minute and in the oil results. If all the conditions of operating remain unchanged, and the candle power falls materially and stays down and the make of gas per minute of run is reduced, the checker bricks should be at once examined and, if dirty, cleaned and removed. Bricks should not be allowed to become so fouled as to make a material reduction in the rate of make. Experience soon teaches an intelligent gas maker to avoid both the extreme of reduced results and of too frequent cleaning.

It is the custom in many works, especially those that are provided with a spare set of apparatus, to change the checker brick at regular intervals, these intervals being measured in some cases by the number of days that the set has been in operation, and in others by the number of hours of work actually done. The object of changing the bricks at fixed intervals in this way is to avoid the irregularities in make and working results that arise from running until it is absolutely necessary to make the change, it being thought the loss due to a day or two of poor working is greater than the slight extra cost involved in cleaning the bricks a little oftener.

In a works that has only one set of apparatus, the bricks should be put in good shape as late as possible in the fall so

that they will be in good condition during the heavy make of December and January. (Trustees.)

Give a description, illustrated with sketches, of one or more forms of the condensers used for cooling illuminating gas during the process of manufacture.

Ans. One of the earliest and simplest forms of condensers used for cooling illuminating gas during the process of manufacture is composed of ordinary cast iron pipes inclined at a small angle to the horizontal and fastened to the side of a wall in such a way that the pipes zigzag back and forth until the ground line is reached. The gas passes through these pipes and radiates its heat into the air until it is cooled down to the temperature of the atmosphere. This form has been elaborated into what is known as the flat screw condenser, in which the inclined pipes are in double tiers and are mounted on frames or standards.

Another simple form of atmospheric condenser is composed of vertical pipes mounted on a cast iron box. The pipes are connected together at the top, in pairs, by return bends provided with cleaning holes, and in the box, partitions sealed in the liquids condensed from the gas, are placed between the pipes joined together by the bends, there being one partition for each pair of pipes. The box is thus divided into compartments into each of which two pipes, which are not connected together at the top, open. At each end is a single pipe opening into a compartment of the box, into which also opens one pipe of a set of two connected at the top. By this arrangement the gas entering at the top of the single pipe at one end passes down into the box and then up and down the pipes alternately until it passes out at the top of the single pipe at the other end of the apparatus.

This condenser has also been elaborated from the simple form containing only a single row of pipes into a condenser containing several parallel rows, the top connection between the pipes being made by properly placed hoods sealed in liquor, the box and partitions at the bottom being substantially the same as in the simple form.

Another vertical atmospheric condenser is the annular

condenser, which consists of a series of large pipes, through the centre of each of which passes a smaller pipe, open to the air at both top and bottom. The gas travels through the annular space between the pipes and imparts its heat to a current of air induced through the centre as well as on the outside of the pipe, the radiating surface being thus nearly doubled. The annular space in one pipe is connected to that of the next by a smaller outside pipe, or pipes, which conveys the gas from the top of one space to the bottom of the next, or vice versa, or else this space is divided into two parts by vertical ribs extending almost the whole length of the pipes, so that the gas passes up on one side and down on the other, and the spaces are connected by short pipes running from the bottom of one to the bottom of the next. If the ribs are arranged to make the gas travel first down and then up, the spaces are connected together at the top instead of the bottom.

Still another form of atmospheric condenser is that known as the battery condenser. This is an oblong box from 2' to 5' wide, 10 to 18' high and of varying length. It is divided internally into compartments by means of partitions leaving openings alternately at the top and bottom, so that the gas entering at the bottom of the first compartment is forced to travel up in this and down in the next until it passes out at the bottom of the last compartment. Tubes 2" in diameter, with both ends open to the air, are run horizontally across the compartments, and the currents of air passing through these tubes assist in cooling the gas. In both the annular and the battery condensers arrangements are made for regulating, in one case the size, and in the other the number, of the openings for the admission of air, in accordance with the temperature of the air and gas at different times.

Atmospheric condensers of one or another of these types are practically the only condensers used in England, but in this country it is considered better practice to employ condensers in which the cooling of the gas is effected by imparting its heat to water. The usual form of such condensers is the ordinary vertical multitubular type. This consists of a cylindrical wrought iron or steel shell from 2' to 8' or 10' in diameter, and from 12' to 20' high, closed at the bottom by a