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CHALK
TALKS

by CARL S. DOW.

Number Seven-Thermometers

A

THERMOMETER is an instrument for measuring intensity of heat. It consists of a glass tube of small bore, with a bulb on the end. The tube and bulb are filled with mercury, and the end sealed. The height of the mercury indicates the temperature.

Kinds

In England and in America the Fahrenheit thermometer is generally used, while in France and in most laboratories in this country the Centigrade is the accepted standard. The difference between the two lies in the graduations. There are other kinds of thermometers, such as the Réaumur; but, as they are not commonly used, we need not consider them.

Graduation

Although various arbitrary units may be adopted for the graduation of thermometers, there are two points which are fixed. These are the boiling point and the freezing point of water.

To graduate a Centrigrade thermometer, it is placed in boiling water, and the height of the mercury column marked: this is called 100°. The thermometer is then held in a freezing mixture, and the height of the mercury marked o°. The distance between these marks is divided into 100 equal parts called degrees.

The graduation of the Fahrenheit thermometer is accomplished in the same way. The boiling point, however, is

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marked 212°, and the freezing point 32°. As shown on the blackboard, there are 180 divisions between the boiling and freezing points.

Comparison of Scales

From the blackboard we know that,

180° F. 100° C.
9° F.
5° C.
1° F.
C.

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1° C.

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This is shown by the lines E F and C D.

Now, let us suppose that the two thermometers are placed side by side and subjected to the same heat. Assume the temperatures to be 176° F. and 80° C., as shown. If heat is now applied and the mercury in the Fahrenheit thermometer rises to 194°, how high will the mercury rise in the Centrigrade thermometer?

The rise in temperature F. will be 194

176 (18) degrees. Since a Fahrenheit degree is of a Centigrade. degree,

10° C.

18° F. because × 18 IO. By adding this to the original Centigrade reading, we get 90°.

Problem

In the above we simply compared a few degrees' change in a case in which the freezing points were not involved.

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Mammoth Remains in Texas

WHILE DIGGING A WELL in the

vicinty of Austin, Texas, a workman recently struck something hard with his pick at a depth of about thirty feet below the surface. The man supposed it to be a stone, and struck it several blows to dislodge it. The blows, unfortunately, caused it to break into two fragments. The object was raised to the surface with the other material of excavation, when the attention of one of the

New Lining for Refrigerator Cars

laborers was attracted to the curious ap- A NEW LINING ("Arctic" brand of Keystone Hair Insulator), especially for refrigerator-car insulation, has recently been placed on the market. Its distinctive characteristic is, that while it possesses the insulating properties of hair felt, it combines the papers used in connection therewith, so that, instead of involving three operations, the "Arctic" can be applied in one. It consists of regular felting hair fastened to and enclosed by two layers of waterproof paper. Tests are said to have demonstrated it to be equal to hair felt, and superior to anything else.

It is furnished in lengths sufficient to reach around a car, and wide enough to extend from the sill to the roof plate. This does away with joints. Car builders will appreciate this saving in labor and waste.

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PART OF A MAMMOTH'S TOOTH RECENTLY UNEARTHED
IN TEXAS.

pearance of the supposed stone. Its surface was grooved in regular lines, and on the side were a number of conical indentations. By the merest chance, a scientist happened to see the fragments, and made a minute examination, with the result that the object was found to be the tooth of a mammoth of unusual size.

few ounces of twelve pounds. In the opinion of experts who have examined it, the tooth has been embedded for many centuries, and much of the roughness of its surface is due to the corroding action of time. A diligent search has been made for other remains of the great animal, but thus far only this part has been found.

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It was taken away and carefully measured and weighed. An idea of the enormous size of the animal from which it came, can be realized when it is stated that the tooth itself is no less than a foot in length and six inches across the broadest portion. Its total weight is within a

For the floors and roofs, the "Arctic" is furnished according to specifications, to fit the nailing strips and car-lines respectively. It is made from 3 inch to 3/4 inch thick, according to the quantity of hair employed, and should meet with ready favor.

The H. W. Johns-Manville Company, 100 William Street, New York, are prepared to figure upon specifications and to

furnish samples, data of tests, etc., promptly upon request.

Improved Dyeing Machine

A RECENT INVENTION in machin

ery used in the dyeing of fabrics, cannot fail to interest a great industry in the United States, so pronounced are its advantages over the present system. The inventor is Mr. Carl Gruschwitz, of Zittau; and the invention applies to that part of dyeing machinery called the "jigger," through which the goods pass at full width in the process of dyeing. The difference from the present method is that the dye is mixed in the vat itself, thereby doing away with the upper construction of reservoirs for that purpose in the present system. The dye is then distributed with force against the cloth by atomizers, instead of the goods passing through a body of liquid.

A Freak Fire Effect

THE 'HE USE of miniature savings banks has become so extensive that they are now manufactured in a very substantial manner, many of them being composed of heavy steel. The one shown in the accompanying picture is made of this metal, and recently passed through an ordeal which shows that these little banks can withstand very high temperatures. It was locked up in a safe in a building which was completely destroyed by the recent fire in Baltimore. The safe itself lay among burning embers and hot ashes for three days before it was taken out of the ruins. After it had been cooled and the doors opened, it was found that the heat had blistered the outside of the little bank, peeling off the enamel in places, and discoloring the surface. The lock, however, was uninjured; and when the bank was opened, the pennies and nickels it contained were found to be in as good condition as when placed in it.

The most remarkable feature of it all, however, was a freak of the fire. Attached to the bank was a circular tag made of stiff paper, containing its number and the name of the owner of the coin it contained. Although, as already stated, the heat was so great that the outside of the bank was badly damaged,

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The Traveling Stairway

IT IS NO LONGER NECESSARY to

climb stairways or to take the ordinary elevator in going from one floor to another. The moving staircase is an invention now in use in many large stores and other buildings. It is really an inclined floor, moving upon a series of small wheels, which, in turn, are operated by larger ones that might be called driving wheels. The surface of the moving floor fits to the surface of the horizontal floor so closely that there is no danger of a person catching his feet between the movable and stationary sections. Any one who wishes to go from the ground story to the one above, simply walks

upon the incline, and, in less than a minute, is carried to his destination. He may remain still on the incline, or walk along it as he pleases. The motion is so uniform that there is no vibration or jarring; and so rapidly do the stairs operate that one of the devices in New York City will carry 2,000 passengers in an hour to a height of about twenty feet.

The driving wheels, around which the endless floor moves, are usually connected by belting to an electric motor or steam engine. About 22 horse-power are required to carry 600 passengers an hour;

TRAVELING STAIRWAY.

and double this amount to carry 2,000 passengers. Calculations based on actual experience show that by the use of electric motors, it costs but seven cents to carry 1,000 people per hour.

Sawing by Compressed Air

A NEW INVENTION which has re

cently appeared in the West, introduces the use of compressed air for operating a saw. This appliance, known as the "Redfield pneumatic engine and frame," is adapted for operating drag saws, for cutting logs, cord wood, heavy timber, and for general use in timber and log camps, displacing the handpower equipment.

Compressed air to operate the engine and saw can be obtained by using a compressor driven by steam, belt, gasoline, or electricity, or by using an ordinary locomotive air pump attached to the boiler of any logging or portable engine.

The pneumatic engine is capable of making from 125 to 150 strokes per minute, depending upon the pressure of air used. At 60 pounds' pressure it will develop 22 horse-power. The engine, constructed almost entirely of brass and steel tubing, weighs 50 pounds. It is claimed for the valve motion-which is of an entirely new design-that it has no complicated valves or parts to get out of order, and that it is very simple and easy of adjustment. The frame is made of machine steel and wood, and, though light in weight, is strong and durable.

It is claimed by the makers that one man with one of these machines can easily cut ten cords of 2-foot wood per day, or 50,000 feet in logs, reducing the present labor expense at least fifty per

cent.

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The McCloud River Lumber Company have given the machine a thorough test and it has proved very satisfactory.

The Acousticon

WITH

WITH THE HELP of this ingenious device the invention of Mr. Miller R. Hutchison, of New York City-it is claimed that any deaf person, save one whose auditory nerve is paralyzed, can be made to hear. Fortunately, even among deaf mutes, there are comparatively few who are absolutely shut out from the reach-at least of some faint echo of sound waves from the outer world. Deafness is in many cases only partial, being due to lack of, or defectiveness in, subsidiary parts of the ear mechanism, while the essential parts may be present in perfect working order. In such cases, what is needed is not an instrument that will merely amplify sounds, but one that will do the work of the missing or defective organic parts. It is on this principle that the "acousticon" is based. The instrument performs the function of the middle ear. In this airfilled cavity, as every student of physiology knows, are located the "ossicles"

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