each of the several States and by the Federal Government, throughout our entire history. There is not a practical educator, college president, or trustee in the land who will not appreciate the importance and utility of such a financial history of higher education in America.

(4) The monograph further shows the progress, development, and present tendencies of higher education in these United States. The history is given of West Point Military Academy, of the Naval Academy at Annapolis, of the Congressional Library, of the Smithsonian Institution, the National Museum, and of the United States Bureau of Education, together with all the financial relations of the General Government towards science and education since the beginning of our life as a nation.

These matters are here communicated to the assembled superintendents of education from all parts of the Union because it is important that you should appreciate their scope and significance, and because you are in a position to strengthen and uphold the highest work of the Bureau of Education. The bureau was originally founded, in the year 1867, "for the purpose of collecting such statistics and facts as shall show the condition and progress of education in the several States and Territories" (Barnard's First annual Repor1, 1867–68, p. 63. Garfield's speech). What better method could there possibly be of showing the condition or progress of education in these United States than by an historical review of the origin, growth, development, and present tendencies of American institutions of learning, beginning with the highest, as did our forefathers, with colleges and universities, and gradually enlarging the horizon of inquiry until the whole field of secondary and common school education is embraced in the retrospect? The broadening plains are best seen from the hill-tops. Unless American educators see to it that the higher education is properly recognized in our State and National reports, our whole system of educational inquiry will degenerate into common school statistics and essays on pedagogical methods. The Bureau of Education ought to take a commanding place in the educational work of the country. By the highest kind of original investigations, at home and abroad, it ought to win the respect and confidence of the best men engaged in educational work, whether college presidents or superintendents of schools. Why is it that the interests. of labor and agriculture can be raised to the dignity of Departments in the United States Government, with a Secretary of Agriculture holding a Cabinet office, while the educational interests of the Republic are allowed to remain upon a lower level? Simply because the educators of the country are content with that level, because they do not exert one-half the compelling energy of either the farmers or the laborunions. The Bureau of Education ought to become a ministry of public instruction, with a recognized place in the Cabinet, and with a constantly energizing influence proceeding from the capital of this country throughout the length and breadth of the land, stimulating the colleges and the universities, as well as the school systems of the whole country,

by publishing the results of organized inquiry. The present Commissioner of Labor touches the vital interests of American labor and of all American society by his reports on the condition of working classes and on the statistics of divorce. The bureau can attain an honorable and influential position in the educational life of the country only by keeping the vantage ground already gained, by pursuing higher lines of activity, by pressing boldly forward for larger appropriations and higher objects, and by enlisting the cordial support of the best friends of ed ucation throughout all these States. Thus gradually the pressure of public opinion will be brought to bear upon Congressmen, and Congress and the nation will recognize at last that the interests of public educa tion are quite as important to the entire American people as are the interests of any one class, like our American farmers or our American workingmen, however honorable the aims of both classes may be.

Strengthen all existing foundations of the higher education in America, whether in the individual States or at Washington. Bring the representatives of public school systems and of our American colleges and universities into more hearty and efficient alliance. Co-oper ate with every respectable agency for the higher education of the American people, whether by summer schools, teachers' institutes, the distribution of good literature in popular form, or by the institution of home reading circles and university extension lectures, now so popular in the manufacturing towns and mining districts of England. Break down the antagonism between mental and manual labor. Make industrial and technical education as honorable as classical culture and the learned professions. Teach the science of government and social science, European as well as American history, in the public school. Then shall we all have greater respect and toleration for our fellowmen; then will all begin to appreciate the necessity of supporting all forms of education, even the highest, by the combined efforts of society and the State. A noble popularity must be given to science and art in America. The people of every State should be led to see that the higher learning is not for the benefit of a favored few, but that it is beneficial and accessible to the sous of citizens, of whatever station. In the proper co-ordination of the common school system with the high school and university, the Western States are leading this Republic to a more thoroughly democratic state of society, with fewer artificial distinctions of culture, with more of the spirit of human brotherhood than the world has hitherto seen. The Eastern colleges and universities will continue to train professors and to develop science, but the West and South will apply both men and ideas to democratic uses. The whole country needs this popularization of culture. With universal suffrage and the sovereignity of the people at the basis of our political life, popular intelligence must be cultivated so that it may be both able and willing to hold fast all that is good in human history, not only civil and religious liberty, but all that makes for happiness and righteousness in a great nation.

THE MOLECULAR STRUCTURE OF MATTER.*

By WILLIAM ANDERSON.

Five years ago, at Montreal, in his address to the Mathematical Section, Sir William Thomson took for his subject the ultimate constitution of matter, and discussed in a most suggestive manner the very structure of the ultimate atoms or molecules. He passed in review the theories extant on the subject, and pointed out the progress which had been made in recent years by the labors of Clausius, of Clerk Maxwell, of Tait, and others,-among whom his own name (I may add) stands in unrivalled prominence. I will not presume to enter the field of scien tific thought and speculation traversed by Sir William Thomson. I propose to draw attention only to some general considerations, and to point out to what extent they practically interest the members of this Section.

In a lecture delivered at the Royal Institution last May, Professor Mendeléeff attempted to show that there existed an analogy between the constitution of the stellar universe and that of matter as we know it on the surface of the earth, and that from the motions of the heav enly bodies down to minutest inter-atomic movements in chemical reactions, the third law of Newton held good, and that the application of that law afforded a means of explaining those chemical substitutions and isomerisms which are so characteristic, especially of organic chemistry. Examined from a sufficient distance, the planetary system would appear as a concrete whole, endowed with invisible internal motions, travelling to a distant goal. Taken in detail, each member of the system may be involved in movements connected with its satellites, and again each planet and satellite is instinct with motions which, there is good reason to believe, extend to the ultimate atoms, and may even exist, as Sir William Thomson has suggested, in the atoms themselves. The total result is complete equilibrium, and, in many cases, a seeming absence of all motion, which is, in reality, the consequence of dynamic equilibrium, and not the repose of immobility or inertness.

The movements of the members of the stellar universe are many of them visible to the naked eye, and their existence needs no demonstration; but the extension of the generalization just mentioned to sub

* Presidential address before the Mechanical Science Section of the British Association A. S., at Newcastle, September, 1889. (Report of British Association, vol. LIX, pp. 718-732.)

stances lying (to all appearances) inert on the earth's surface is not so obvious. In the case of gases, indeed, it is almost self-evident that they are composed of particles so minute as to be invisible,-in a condition of great individual freedom. The rapid penetration of odors to great distances, the ready absorption of vapors and other gases, and the phenomena connected with diffusion, compression, and expansion seem to demonstrate this. One gas will rapidly penetrate another and blend evenly with it, even if the specific gravities be very different. The particles of gases are (as compared with their own diameters) separated widely from each other; there is plenty of room for additional particles; hence any gas which would, by virtue of its molecular motion, soon diffuse itself uniformly through a vacuum will also diffuse itself through one or more other gases, and once so diffused, it will never separate again. A notable example of this is the permanence of the constitution of the atmosphere, which is a mere mixture of gases. The oxygen and the nitrogen, as determined by the examination of samples collected all over the world, maintain sensibly the same relative proportions, and even the carbonic acid, though liable to slight local accumulations, preserves, on the whole, a constant ratio, and yet the densities of these gases differ very greatly.

Liquids (though to a much less degree than gases) are also composed of particles separated to a considerable relative distance from each other, and capable of unlimited motion where no opposing force-such as gravity-interferes; for under such circumstances their energy of motion is not sufficient to overcome the downward attractions of the earth; hence they are constrained to maintain a level surface. The occlusion of gases without sensible comparative increase of volume shows that the component particles are widely separated. Water (for example) at the freezing point occludes above one and three quarter times its own volume of carbonic oxide, and about 480 times its volume of hydrochloric acid, with an increase of volume in the latter case of only one-third. The quantity of gas occluded increases directly as the pressure, which seems to indicate that the particles of the occluded gas are as free in their movements among the particles of the liquid as they would be in an otherwise empty containing vessel. Liquids therefore are porous bodies whose constituent particles have great freedom of motion. It is no wonder consequently that two dissimilar liquids, placed in contact with each other, should interpenetrate one another completely, if time enough be allowed; and this time, as might be expected, is con. siderably greater than that required for the blending of gases, because of the vastly greater mobility of the particles of the latter. The diffu sion of liquids takes place not only when they are in actual contact, but even when they are separated by partitions of a porous nature, such as plaster of Paris, unglazed earthenware, vegetable or animal membranes, and colloidal substances, all of which may be perfectly water-tight, in the ordinary sense of the term, but powerless to prevent

the particles of liquids making their way through simultaneously in both directions.

When we come to solid substances the same phenomena appear. The volumes of solids do not differ greatly from the volumes of the liquids from which they are congealed, and the solid volumes are generally greater. The volume of ice (for example) is one tenth greater than the water from which it separates. Solid cast-iron just floats on liquid iron, and most metals behave in the same way; consequently, if the liquids be porous the solids formed from them must be so also; hence, as might be expected, solids also occlude gases in a remarkable manner. Platinum will take up five and a half times its own volume of hydrogen, palladium nearly 700 times; copper, 60 per cent.; gold, 29 per cent.; silver, 21 per cent. of hydrogen, and 75 per cent. of oxygen; iron from 8 to 12 times its volume of a gaseous mixture chiefly composed of carbonic oxide. Not only are gases occluded, but they are also transpired under favorable conditions of temperature and pressure, and even liquids can make their way through. Red-hot iron tubes will permit the passage of gases through their substance with great readiness. Ordinary coal gas-when under high pressure-is retained with difficulty in steel vessels, and it is well known that mercury will penetrate tin and other metals with great rapidity, completely altering their structure, their properties, and even their chemical compositions.

The evidence of the mobility of the atoms or molecules of solid bodies is overwhelming. Substances when reduced to powder, may even at ordinary temperatures be restored to the homogeneous solid condition by pressure only. Thus Professor W. Spring some ten years ago produced from the powdered nitrates of potassium and sodium-under a pressure of thirteen tons to the square inch-homogeneous transparent masses of slightly greater specific gravity than the original crystals, but not otherwise to be distinguished from them. More than that, from a mixture of copper filings and sulphur, he produced-under a pressure of thirty-four tons per square inch-perfectly homogeneous cuprous sulphide (Cu2 S), the atoms of the two elements having been brought by pressure into so intimate a relation to each other, that they were able to arrange themselves into molecules of definite proportion; and still more remarkable, the carefully dried powders of potash, saltpeter, and acetate of soda, were by pressure caused to exchange their metallic bases, and form nitrate of soda and acetate of potash.

At high temperatures the effects are more easily produced on account of the greater energy of motion of the atoms or molecules. In the process of the manufacture of steel by cementation, or in case-hardening, the mere contact of iron with solid substances rich in carbon is suffi cient to permit the latter to work its way into the heart of the former, while in the formation of malleable cast-iron the carbon makes its way out of the castings with equal facility; it is a complete case of diffusion of solid substances through each other, but on account of the inferior