apothecaries, alchemists, and astrologers of the Middle Ages, given over largely to the search for the philosopher's stone, and to the manufacture of elixirs, drugs, charms, cosmetics, etc. With the fifteenth century came the reaction against Scholasticism; and men began to study nature rather than books, they began to observe rather than to deduce facts and principles, and by the end of the sixteenth century the experimental method was well established.

In 1589 Galileo demonstrated the necessity of the experimental method at Pisa. Climbing the leaning tower, he let fall a weight of one pound and a weight of one hundred pounds; starting simultaneously, the weights struck the ground together, at once and forever disproving the Aristotelian deduction that the speed of falling bodies was proportional to their weights. Francis Bacon, in 1620, and Comenius, in 1630, set forth arguments for the inductive method and the experimental investigation of facts. But prior to the nineteenth century all laboratories were private institutions devoted wholly to research. In 1824 Purkinje established a physiological laboratory in Breslau; in 1825 Liebig established a laboratory of chemistry, medicine, and physiology in Giessen; in 1845 Lord Kelvin -then William Thomson-opened a physical laboratory in the University of Glasgow; in 1849 a pharmacological laboratory was created by Buchheim; in 1856 Virchow opened a pathological laboratory in Berlin. As the work of the laboratories has developed, there has come about a specialization of the problems to be undertaken, and as a result new research laboratories are founded every year.

Laboratories for instruction do not differ materially from research laboratories as far as equipment and method is concerned.

CHEMICAL LABORATORIES. The appearance of the earliest chemical laboratories is familiar, since they formed attractive subjects for the contemporary artists. Not merely were these laboratories used for experiment, but also for the teaching of pupils and assistants. At present, any well-lit room, supplied with water, gas, electricity, and a hood communicating with a flue to carry off noxious gases, may serve for almost all chemical work. The water-supply operates vacuum-pumps, and can be made to furnish air under pressure by means of a tromp; power can be obtained either from small water or electric motors, and the gas furnishes heat. Much chemical work, both scientific and technical, is carried out in such laboratories, originally built for other purposes. The most important chemical laboratories, however, are buildings, constructed entirely for chemical work, in connection with the great universities and schools of science, and are intended both for investigation on the part of the instructors and advanced students and for the regular instruction of the mass of the students. The wide extension of this class of laboratories began with the famous laboratory erected by Liebig at Giessen in 1825, after which teaching-laboratories, each showing an advance on the preceding, sprang up at almost all the German universities and quickly reached a high degree of excellence.

The laboratory buildings are divided into rcoms of varying sizes, each room assigned to one or more branches of chemical science, so that each student passes, during his course, through

most of the rooms. In France a less systematic arrangement, avoiding large rooms, is preferred by some chemists. The number of the rooms and the branch of chemistry to which each is dedicated vary with the size of the building and the importance assigned to different subjects and to teaching and investigation respectively. Many laboratories consist of a large lec ture-room, a large room for simple inorganic preparations and qualitative analysis; another large room for quantitative analysis and inorganic research; a third large room for organic chemistry; and a number of small rooms to serve as class-rooms, library, balance-rooms, private laboratories and offices for the instructors, for gas and water analysis, for physical chemistry, as furnace-room, combustion-room, hydrogen-sulphide room, storerooms, toilet-rooms, etc. In some cases separate buildings are provided for particular branches of chemistry. For example, the University of Göttingen has a sepa rate building for physical chemistry.

In the larger laboratories almost every branch of chemistry has its separate room. Few general principles can be laid down for the plan of the building and the relation of the rooms to each other. The first consideration is to obtain abundant light. Everything should give way to this. Next the office and private laboratory of each professor should be central with reference to the rooms under his care. However, when permanent and responsible assistants are in immediate charge of the large rooms, this consideration is of less importance. Of course, such rooms as balance-rooms, combustion-rooms, and hydrogen-sulphide rooms, must be close to the large rooms to which they belong. Special considerations will decide the position of various rooms. Thus, a furnace-room is placed on the lowest floor to get the advantage of a high chimney. All chemical laboratories are elaborately piped. There is usually one system for gas used in heating, another for gas used in lighting, and often a third for certain specially protected gas-jets, which are required to burn continuously for long periods. This permits the rest of the gas to be turned off every evening at the close of work. Water is carried, not merely to each room, but commonly to each desk. Where the water is supplied under a strong pressure, injector vacuum-pumps are used, but when this is not the case, the whole building must be supplied with pipes connected with a vacuum steam-pump. In any case such a pump, with connecting pipes to each desk, is almost a necessity in the organic laboratory, for distilling under reduced pressure. Another steam-pump supplies a series of pipes, carrying air under pressure. There are steam or hot-water pipes for heating and pipes for steam at high pressure for heating stills, water-baths, and steam-closets. In addition, in some laboratories distilled water is distributed to the different rooms, by a system of block tin pipes. Formerly oxygen was distributed to several points by pipes, but the introduction into commerce of compressed oxygen in strong steel cylinders has made this system obsolete. Hydrogen-sulphide gas is also carried, in most cases, by pipes to several rooms. The system of pipes for carrying off waste water must be carefully planned. Ordinary plumbing is destroyed in a few years by acids and compounds of mercury. An excellent plan is to carry the

waste water by open troughs to the vertical earthenware main pipes, so avoiding leadwork altogether. The system of flues for ventilation of the hoods must be carried over the whole building. This system may be connected with a lofty chimney, or with a rotary fan. Electricity is usually supplied, for scientific purposes, from accumulator batteries.

Each student working in a room has a locked desk for his own use. The desks are usually supplied with gas, water, vacuum-pumps, draught-, closets, apparatus, and reagents, so as to reduce to a minimum the cases in which it is necessary for the student to leave his desk. Space is economized in most laboratories, in the rooms set apart for beginners, by dividing the space under each desk into two independent closets, so that two students may use the same desk at different hours or on different days. In the larger laboratories much special apparatus is found, such as a machine for producing liquid air, grinding mills driven by power, working models of chemical industrial works, and apparatus for treating

materials on an industrial scale.

The technical laboratories maintained by industrial establishments may be simply for analytical work, in which case they may be modeled after the rooms for quantitative analysis in the teaching laboratories; but in cases where experimental work is carried on, the plan is quite different. Power must be supplied more freely, facilities provided for handling larger quantities of material, and liberal space left free to set up working models of apparatus on a large scale. See section on Engineering Laboratories.

PHYSICAL LABORATORIES. Rooms specially equipped for physical experimentation were not provided until long after well-organized chemical laboratories were in use. Such early experimenters as Boyle, Newton, and Franklin made use of their own living apartments for their experiments, and it was not until well into the nineteenth century that professors of physics obtained separate rooms in which they could carry on work with due convenience. The next step was for these professors to admit students to their own laboratories, and to direct their research. At Heidelberg the first physical laboratory was opened in 1846, two rooms being devoted to instruction in practical physics. The laboratory at the University of Glasgow where original research was carried on by students under the direction of Lord Kelvin was also one of the earliest of these laboratories. In France, in spite of the brilliant work done in private laboratories in the first half of the nineteenth century, the facilities for systematic work by students were hardly as ample as in Germany, but by 1868 it was realized that additional accommodations for students and research laboratories for professors and skilled investigators were essential. One result of this movement was the foundation, in the Sorbonne in Paris, of a physical laboratory, of which Jamin was made director, and which has been celebrated not only for his researches, but also for those of Lippman. This laboratory was placed under the direction of the faculty of science in 1894 and was then remodeled. King's College, London, also adopted regular laboratory training as part of its work in physics about this time, and three rooms in its building were used as a laboratory. The first building in England specially designed for

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the study of experimental physics was structed at Oxford, under plans of Prof. Robert B. Clifton. This was followed by the Cavendish Laboratory at Cambridge, built in 1874 by Prof. James Clerk-Maxwell, who incorporated in it many of Professor Clifton's ideas. In the United States the progress was naturally slower than in Europe, but it is asserted that the first institution to make laboratory physics a part of its regular educational work was the Massachusetts Institute of Technology, in Boston. The systematic work begun at the Massachusetts Institute of Technology in practical physics furnished an example which was soon followed by other American colleges, including Cornell and Harvard, and even by many high schools, and so rapid was the progress made that in 1886 Harvard required experimental work in physics in its entrance examinations.

A

In elementary laboratory work in physics, the apparatus is simple and the results demanded are qualitative rather than quantitative. laboratory for this purpose would be merely one or more rooms provided with suitable tables. The simple apparatus used should, where possible, be constructed by the student himself, the use of tools for the making, adjusting, and repair of apparatus forming not the least valuable part of the training. The ordinary manipulation of glass tubes, and the use of the more common wood-working tools, as well as of a few implements for cutting and shaping metal, must be learned by the student at an early stage.

The entrance requirements for the colleges have set the standard for the physical work to be done in preparatory schools. No elaborate instruments are required for such courses, and it is considered better practice to have the student work as accurately as possible with somewhat crude apparatus. In the college laboratory the equipment is of a much higher grade, and should be as extensive as the means of the institution will permit. The student here begins to work quantitatively, and accuracy of observation and measurement is the prime essential of his work. The usual method of instruction is to have an elementary course which covers the essential features of physics. That is, a student will begin with the ordinary measurements of length, mass, and time. He will perform quantitative experiments in sound, heat, light, and electricity. There must be at his disposal measures of length and micrometers of various forms which will enable him to determine length or thickness to one-hundredth of a millimeter, or even less. He will also have analytical balances for determining the mass of substances with an accuracy of the one-hundredth of a milligram, and such other instruments as accurately calibrated thermometers, standards of electrical resistance carefully determined, and optical apparatus in which the graduated circles and other parts used for measurement are of high precision. As the construction of this apparatus involves considerable mechanical skill, it is, of course, impossible for the student to make it; but its test and calibration is one of his first tasks. He is taught the necessity of correcting his observations and looking for and compensating for such causes of error as can be detected, and, in short, to attain as great accuracy as the apparatus he uses is capable of. For elementary laboratories no extensive and peculiar structural features are required in the

building. Suitable brackets firmly fastened to brick walls furnish supports for the more sensitive apparatus, and convenient sinks and water and gas piping and electric fittings are provided. In most colleges and universities, however, these elementary laboratories are in the same building as research laboratories for the staff and advanced students, and as a result they contain many features not absolutely essential for work of this description. In building physical laboratories for research work, every other consideration is, or should be, sacrificed to direct' utility. Stone piers on which such instruments as galvanometers are set are independently founded and carried up through one or more floors, without any connection whatsoever with other parts of the building. Stone tables or slabs for similar purposes are built in the brick structural walls of the building. High towers for experiments with pendulums, pressures of liquids, and falling bodies are another feature of a modern laboratory, and in most cases they, too, are built on an independent foundation. The building is usually arranged so that it has the best possible light, especially as regards direct sunlight. For certain work electrical or other power is desirable, and a system of pipes, wiring, and shafting is carried about the building. Another feature is a constant-temperature room in the cellar, usually where the astronomical clocks and other instruments which must be maintained at or near the same temperature the year around are installed. In short, the greatest care is observed in adapting the building for its use as a place of research, and every convenience is placed at the disposal of the student. It must be stated, however, that many physicists do not altogether approve of such refinements of laboratory construction, and think that the ability to overcome difficulties is a valuable part of the training. Furthermore, the very nature of the refinements may in some cases constitute serious causes of error. For example, an independent tower or pier may act as an inverted pendulum and have a period of vibration of its own. But be this as it may, it is undoubtedly true that at the German universities, where the greatest facilities have been introduced into the buildings and are put at the disposal of the students, the best work is carried on. The laboratory belonging to the University at Strassburg, and that of the Polytechnikum at Zurich, are typical of the best progress in modern laboratory construction, although Berlin and a number of other German universities are not far behind.

But important physical research has also been carried on in laboratories outside of educational institutions, and the more celebrated of these deserve brief mention. The laboratory of the Royal Institution in London was founded in 1800 by Count Rumford, and although the original intention of its founder was the furtherance of applied science, it soon became the home of the most brilliant and original investigations in the realm of pure science, carried on by such men as Sir Humphry Davy, Faraday, Tyndall, Rayleigh, and Dewar. In 1896 the research facilities of the Royal Institution were increased by the opening of the Davy-Faraday Research Laboratory, which has been most successfully conducted by Lord Rayleigh and Prof. James Dewar. In Germany the most important work has been carried on at the Reichsanstalt, or physico-techni

cal institution, at Charlottenburg, near Berlin. Through the munificence of Werner Siemens, who in 1884 gave about $125,000 to the institution, and through appropriations by the Reichstag, suitable buildings were erected, and from 1888 to 1894 the laboratory was directed by Helmholtz. The influence of the Reichsanstalt on industrial conditions in Germany has been most valuable. Various standards are here made, instruments are calibrated, and certificates which have a world-wide acceptance are given to the apparatus which complies with the standards of the bureau. Technical research is also carried on, and many valuable papers are published from time to time from the bureau. Various instruments of glass are examined, and the work of the Germans in this field has been raised to a high degree of excellence, with the result that the manufacture of optical instruments has greatly increased. The same holds true in the case of electrical apparatus, and the standards of resistance and other apparatus also have been made of a high grade of precision. In Paris there is the Conservatoire des Arts et Métiers. With the purchase of a physical cabinet, a department of physics was or ganized in 1829, which has since been increased and developed, and furnished a home for important researches. Perhaps the most celebrated labora tory in France is the International Bureau of Weights and Measures, organized in 1875 by the coöperation of eighteen different nations. Here are prepared for distribution to the subscribing nations the various metric standards of length and mass; the meter and kilogram of the archives with which the secondary or natural standards have been compared are preserved. In this laboratory are carried on the most elaborate comparisons of standards and instruments, and the work of this bureau has been invaluable to workers in science in many departments. A national physical laboratory was established in Great Britain during the closing years of the nineteenth century, and to it in 1900 was given a building and site near London, its control being given to the Royal Society. Here a beginning has been made of supplying means for important physical investigations, and the equipment is being rapidly increased. In the United States, in 1901, the National Bureau of Standards was established by act of Congress, approved March 3, 1901; it is designed to possess a similar function to the Reichsanstalt and the National Physical Laboratory of England. In 1903 a building was being erected for the laboratory of this bureau, and active plans had been made for its investigations. By law it is given the custody of the national standards, and will issue secondary standards for the use of industrial and scientific workers. So valuable and important has been the work of similar institutions in Europe that the National Bureau of Standards was demanded by united scientific and manufacturing interests.

ENGINEERING LABORATORIES. The success which has attended chemical, physical, and other laboratories organized either for instruction or research has led to the establishment of engineering laboratories in which the student is taught to apply himself particularly to such problems as he would encounter in the actual practice of his profession. Such laboratories are also used by advanced workers to study experimentally such difficulties as are encountered in daily life, with the hope of finding simpler and more eco