Physical The housing and equipment of a physical laboratory is of very great importance. The building in which the laboratory is to be located should 'be so situated as to reduce to a minimum alljar and tremor, and to do away with all outside magnetic dis turbances, such as those due to electric car lines.
Many rooms are needed for special divisions of the work; such as constant temperature rooms, which require special precautions in de sign and construction and which are best situ ated below ground. Special rooms are de manded for radiometers, spectrometers, poten tiometers and such other instruments as re quire constant conditions to ensure good results. Dark rooms are necessary for work in light, which includes experiments requiring diffrac tion gratings, photometers and the phenomena of light in general. Since photography has be come of very great practical importance, fully equipped dark rooms are desired; also a sky light room where enlargements and reductions of negatives may be made, and lantern slides prepared. It should be possible to introduce sunlight into some of the rooms.
A lecture-room in which experimental dem onstrations may be given is a necessity, and much attention should be given to its arrange ment. The lecture-room should be well lighted but should be provided with arrangements for readily darkening it. The experimental lecture table should be placed so as to be easily seen from all parts of the room. This table should have water, gas, air blast, suction, water motors and other motors, sink and terminals for ob taining direct and alternating currents. solid masonry pier upon which to set up deli?k.
cate apparatus and that requiring no vibration should be provided. The table tops should be impervious to water and so far as possible acid resisting.
An apparatus-room in which is kept demon stration apparatus should be situated conveni ently to the lecture-room; general apparatus may also be kept there. The opening between the apparatus-room and the lecture-room should be large enough to admit the passage of large pieces of apparatus, and also to allow experi ments to be set up oh wheeled tables in the apparatus-room, then wheeled directly into the lecture room.
Separate rooms should be provided for re search work. It is desirable that it be possible to connect some of the rooms in suites and to provide dark rooms for some of the suites.
Research-rooms should contain water and gas, both ordinary illuminating and acetylene gas. They should have electrical connections to a central switchboard sufficient to obtain various types of current at one time. The floors of the building should be solid. Stone tables built in the walls form good supports for instruments, but there should be provided in some cases stone piers with independent foundations.
The general laboratories should have plenty of light and should be provided with separate rooms for some classes of work, as in light and sound, where it is often necessary to have dark ened rooms. A heat bench or table should be provided; it should have an impervious top with enough pitch to drain into a central trough or hole to conduct away the waste. A rack with hooks above the bench, from which to sus pend thermometers, is convenient. The rooms should be well supplied with tables, and along the walls stone shelving built in the walls will be found useful. The dirt incident to primary batteries may be concentrated if all the cells be kept together, their terminals leading to a switchboard to which are connected the termi nals of lines leading to the various stations in the rooms.
The laboratory should also have storage bat teries, and, if necessary, have its own dynamos in order to procure direct and alternating cur rents. An acetylene gas plant, and a com pressor and liquefier for obtaining liquid air and other gases, are becoming necessary parts of the general equipment of a physical labora tory. A plant for the production of oxygen and hydrogen is also often desirable. A workshop in which to repair and build apparatus is a great convenience. The wiring and plumbing should be open and accessible as possible. All dark rooms as well as other rooms should be well ventilated, as it is often imperative for an ob server to be confined in a room for hours at a time. Further reference to physical laboratory equipment will be found under the head of Electrical Laboratory.