pure line by selection alone, that is, without out-crossing, is precluded. This is illustrated in a study of the effects of selection with respect to the chemical character of the oil of a pureline strain of soy beans (Figure 5). Selections respectively from the highest and from the lowest plants with respect to the degree of saturation of the oil, carried on for a period of four years, have produced no hereditary effect-the progeny of both lines of selection continue to vary over the same range.

THE SEARCH FOR FACTORS.

By far the greater number of characters of economic importance are of the complex sort, dependent upon several to many

factors. The big task is to analyze such characters to identify the factors and learn how they are inherited. Such indefinite characters as milk and meat production offer especial difficulties but a beginning is being made even with these. Jersey cattle, representing the most refined dairy type, and Polled Aberdeen Angus, a specialized beef type, were crossed, not with the idea of producing a new breed, nor in fact with any immediate practical object in view, but in order to learn what characters are independent and what go together; what ones, if any, be

have in simple Mendelian fashion and what ones are complex— in short, to make just such an analysis as has been suggested. One other example may serve to show the nature of these investigations. Last year Professor L. R. Jones read before this society a paper in which he described his successful attempts to breed a strain of cabbage resistant to the disease known as "yellows." His experiments demonstrated clearly that there is a distinct heritable difference between the resistant and the non-resistant strains. We are now engaged in studying the method of inheritance of this difference. While the experiments have not yet gone far, they seem to show clearly that resistance in this case is not a simple character, but depends upon several, perhaps many, heritable genes. A knowledge of these factors would greatly facilitate the production of a resistant strain that would "breed true." Flax wilt is caused by an organism similar to that which causes cabbage yellows, and flax offers much better opportunities for investigation. If susceptible and resistant strains of flax are crossed, the first generation offspring are usually even more vigorous and fully as resistant as their resistant parents. (Figure 6). In the second generation, however, there is a great variability, and here again the indications are that at least several factors must be present to make a flax plant able to withstand successfully the attacks of the parasitic fungus which causes the wilt.

Jones, L. R. "Some Recent Advances in Plant Pathology," SCHOOL SCIENCE AND MATHEMATICS, Vol. 17, No. 2, February, 1917, pp. 95-100.

WHY YOU MUST BUY LIBERTY BONDS.

War is a glutton that lives on lives and riches. There is no limit to the devouring greed of war. As long as there is an unconquered life, or an undevoured dollar, war is hungry.

When war attacks a nation there is no choice every able-bodied man knows that he must fight-now or later. Selective drafts may miss a man here and there for a few months, but if the war goes on, a time comes when every man who can walk and carry a gun must go to the colors and fight for the very life of his country, his family, himself.

Remember these things. The nation has a right to take absolutely every dollar of property in the United States for the life and death war against tyranny, autocracy, slavery, and foreign aggression and vassalage. But the nation does not intend to exercise that final and desperate right. No! The Government says: "The nation is fighting for its life. Lend us your money. We will give you Liberty Bonds, secured by all the wealth and sovereign taxing power, bearing 4 1-4 per cent interest, and protected by a good sinking fund, with tax exemptions to make the loan better. Avoid the extreme necessity. INVEST IN ALL THE LIBERTY BONDS YOU CAN."

IS HIGH SCHOOL SCIENCE ON THE DECLINE?

Editor, SCHOOL SCIENCE AND MATHEMATICS:

In the March number of your journal, page 249, I made the ollowing statement: "A study of the reports of the Commissioner of Education for the past twenty years, incomplete though those reports are, leads to the conclu ion hat the total percentage enrollment in high schol science subjects did decline from about 1890 to 910, bu from 1910 to 1915 there was a slight increase." This tatement has been challenged by a scientist who e word carries much weight. I should like a little space in which to present the facts upon which i base my conclusion.

On page 487, Volume II, Repor of the Commissioner of Education for 1916, under the heading, "Student in Certain Studies in Public High Schools Since 1890," we find the following data:

Astronomy.
Physics...

Chemistry....

PER CENT OF TOTAL ENROLLMENT.

Physical geography.

Zoology.

Botany..

General biology.

Geology...

Physiology..

Dom stic economy

Agricu'tu e

Totals....

.32.31 95.55 83.94 69.46 91.14 85.74

In considering these data we should keep the following points in mind: 1. stronomy and geology were more generally tudied in 1890 than at any later date.

2.

Physical g ography, botany, oology, and physiology were also well recognized high school subjects in 1890.

3.

That many scienti ts hesitate to include all of the teaching of agriculture and domestic economy as science instruction.

4. That general science has never been listed by the Commissioner in his reports.

5. Finally, we should also remember that the fourteen-weeks courses of 1890 and 1895 have generally given place to eighteen-weeks courses or one-year courses in 1915. Until we have some more reliable source of information, I think we shall do well to draw our conclusions from these figures from the Commissioner's reports regarding percentage enrollment in high school subjects. FRED D. BARBER.

CONCRETE HAS MANY USES. Concrete, because of its great resistance to fire and to the shock of explosions, is adaptable to a wide variety of uses, according to the United States Geological Survey Department of the Interior. It is cheap, easily and quickly handled, sanitary, and durable, and its characteristics render it of great military importance. Among the military uses to which concrete is put are the construction of armories, barracks, roads, bridges, coast and interior fortifications, gun emplacements, trench linings, bombproof shelters, magazines for explosives, tunnels, retaining walls, sea walls, wharves, dry docks, water reservoirs, aqueducts, sewers, sewagetreatment works, incinerators, stables, floors, roofs, munition-factory buildings, warehouses, fuel-oil tanks, barges, and even in the interior of battleships.

HOW MISSISSIPPI GOT HER HILLS.

Is Mississippi a plain or a plateau, swampy, undulating, hilly, rugged, or what? How many people know? Precise determinations of altitude made by the Government show that its average height above sea level is several hundred feet, or relatively high for a state bordering the Atlantic or Gulf coast, and its valleys are surprisingly deep.

But the most striking features of the surface of the state are the gullies -little valleys carved in bright-colored sands and clays with sides so steep and upper ends so abrupt that they prevent you from going across country anywhere you like even afoot, and although actually only fifty to two hundred or three hundred feet deep, they seem to be good-sized canyons. If you enter one of the canyons at the lower end or find a place where you can climb down a gully wall, you are hidden from the world and may soon get delightfully lost. You may wander about between walls striped horizontally with red, brown, and cream, a new choice of routes continually presenting itself in the intricate ramifications-the whole like a labyrinth; but just as a tributary stream joins its main only at the lower end, there is, as a rule, only one place where any single gully or passage is connected with another.

Even in the southern end of the state, hills reaching over five hundred feet above sea level, or two hundred or three hundred feet above their bases, and some of the uplands are slashed in every direction by innumerable gullies, laying bare the substrata of varicolored irregular layers of sand, clay, and in places gravel.

Nevertheless there is an immense area of arable and fertile land in Mississippi. The soil is so light that with the considerable slope of the hillsides care must be taken to prevent washing and the growth of gullies, which, though disastrous to farming where neglect allows them a start, make charming scenery and afford the geologist a fine opportunity to decipher the complex and in many ways peculiar history of the state.

A short scientific paper dealing with the character of materials exposed in the gullies and a part of the geologic history of the state has recently been published by the U. S. Geological Survey, Department of the Interior. [U. S. Geological Survey Press Bulletin.

HEAVING OF PAVEMENTS BY FROST.

It has long been known by highway engineers that pavements laid on clay soils are more apt to be heaved by frost than those laid on sand or gravel. This has hitherto been attributed to the fact that less water exists in sand or gravel than in clay directly beneath a pavement. Prof. Stephen Taber, professor of geology of the University of South Carolina, has conducted experiments that undoubtedly upset this old theory.

In a paper on "Pressure Phenomena Accompanying the Growth of Crystals," presented before the National Academy of Science last year, Prof. Taber gives an account of what happens when moist clay beneath a stone freezes. The stone cools more rapidly than the clay, so that ice crystals first form at the points of contact between the stone and the clay. The water in the interstices of the clay itself does not freeze so rapidly as water on the surface of the clay, for the freezing point of water in capillary spaces is considerably below that of water in the open. But the freezing of the thin skin of water on the surface of the clay results in more water being fed up from below, very much as a lamp wick feeds up more oil as fast as the oil at the top burns. Then another thin layer of ice forms on the surface of the clay beneath the first layer of ice, and so on, steadily raising the stone by the building up of a layer of ice between the clay and the stone.

In sand or gravel the same phenomenon does not take place, even when saturated with water. Once the water in the pores of the sand begins to freeze, it freezes progressively downward, because the pores are not so small as to form capillary spaces, and do not, therefore, lower the freezing point of the water.

Experiments were made by Prof. Taber by which the existence of a layer of ice between moist clay and a weight was proved, coincidently with the absence of an ice layer between wet sand and a weight. Hence his theory is established beyond doubt. It also accounts completely for such phenomena as the lifting of blocks of concrete weighing many tons a distance of several inches even when the frost had penetrated the clay soil to a depth of only a few inches.

Highway engineers will not be slow to see the uses to which this new bit of scientific knowledge can be put.-[Engineering and Construction.

STENOGRAPHERS AND TYPEWRITERS WANTED-MEN AND WOMEN.

The United States Government is in urgent need of thousands of typewriter operators and stenographers and typewriters. All who pass examinations for the departments and offices at Washington, D. C., are assured of certification for appointment. It is the manifest duty of citizens with this special knowledge to use it at this time where it will be of most value to the Government. Women especially are urged to undertake this office work. Those who have not the required training are encouraged to undergo instruction at once.

Examinations for the Departmental Service, for both men and women, are held every Tuesday, in 450 of the principal cities of the United States, and applications may be filed with the Commission at Washington, D. C., at any time.

The entrance salary ranges from $1,000 to $1,200 a year. Advancement of capable employees to higher salaries is reasonably rapid.

Applicants must have reached their eighteenth birthday on the date of the examination.

For full information in regard to the scope and character of the examination and for application blanks address the U. S. Civil Service Commission, Washington, D. C., or the Secretary of the U. S. Civil Service Board of Examiners at Boston, Mass.; New York, N. Y.; Philadelphia, Pa.; Atlanta, Ga.; Cincinnati, Ohio; Chicago, Ill.; St. Paul, Minn.; St. Louis, Mo.; New Orleans, La.; Seattle, Wash.; San Francisco, Cal; Honolulu, Hawaii; or San Juan, Porto Rico.

TO THE CITIZENS OF AMERICA.

One million, eight hundred thousand of America's brave sons are now serving in the Army and Navy of the United States. Thousand of them are already upon the battle fields of France, fighting and dying to save the liberties and rights of those who stay at home and to secure democracy and freedom against Prussian brutality and military despotism. Their blood already consecrates the soil of noble France.

Who can think of their heroic sacrifices without emotion?

Who can contemplate their trials and sufferings, their dangers and struggles, without setting ablaze the fires of patriotism in his soul?

Who can look upon the blue jacket of the sailor or the khaki jacket of the soldier without admiration for the indomitable hearts that beat beneath-hearts that may soon be stilled in death as the price they pay to save civilization?