A PHYSICAL LABORATORY INDICATOR.
The difficulties attending the management of a physical laboratory are much greater than those of a chemical one. The cause of this lies in the fact that in the latter the apparatus is less complicated and the pieces less varied. Any contrivance that will reduce the labor and worry connected with the running of a laboratory is valuable.
A physical laboratory may be arranged in several ways. The apparatus may be kept in a store room and such as is needed may be given to the student each day and removed after the experiments are performed; or the apparatus for each experiment or system of experiments may be kept in a fixed place in the laboratory ready for assembling; for certain experiments the apparatus may be kept in a fixed place in the laboratory and permanently arranged for service.
Each student may have his own desk and apparatus or he may be required to pass from desk to desk. The latter method is preferable.
When a store room is used the services of a man are required to distribute and afterward to collect. If the apparatus is permanently distributed, a large room is necessary, but the labor of collecting and distributing is done away with.
There are certain general experiments intended to show the use of measuring instruments which all students must perform. To illustrate the use of the indicator I have selected an elementary class, although the instrument is equally applicable to all classes of experiments.
Having selected a suitable room, tables may be placed against the walls between the windows and at other convenient places. Shallow closets are built upon these tables against the wall; they have glass doors and are fitted with shelves properly spaced. A large number of light wooden boxes are prepared, numbered from one up to the limit of the storage capacity of the closets. A number corresponding to that upon the box is placed upon the shelf, so that each one after removal may be returned to its proper place without difficulty. On the front of the box is a label upon which is written the experiment to be performed or the name of the apparatus whose use is to be learned, references to various books, which may be found in the laboratory library, and the apparatus necessary for the experiment, which ought to be found in the box. If any parts of the apparatus are too large to be placed in the box, the label indicates by a number where it may be found in the storage case.
It is evident that, instead of the above arrangement, all the boxes can be stacked in piles in a general store room. The described arrangement is preferable, as it prevents confusion in collecting and distributing apparatus when the class is large.
The Indicator (see figure).--Some device is evidently desirable to direct the work of a laboratory with the least trouble and friction possible. I have found that the old fashioned "peg board," formerly used in schools to record the demerits of scholars, modified as in the following description, leaves nothing to be desired.
The requirements of such an instrument are these: It must show the names of the members of the class; it must contain a full list of the experiments to be performed; it must refer the student to the book and page where information in reference to the experiments or apparatus may be found; it must show what experiments are to be performed by each student at a given time; it must give information as to the place in the laboratory where the apparatus is deposited; it must show to the instructor what experiments have been performed by each student; it must prevent the assignment of the same experiment to two students; it must enable the instructor to assign the same experiment to two or more students; it must form a complete record of what has been done, what work is incomplete, and what experiments have not yet been assigned; it must also be so arranged that new experiments or sets of experiments may be exhibited.
A, B, C, etc., are cards upon which are the names of students. 1, 2, 3, etc., are cards like the one described in the article. The small circles represent unassigned experiments. The black circles (slate nails) represent work done. The caudate circles (brass nail) represent work assigned.
The indicator consists of a plank of any convenient length and breadth. The front surface is divided into squares of such size that the pegs may be introduced and withdrawn with ease. At each corner of the squares holes are bored into which nails may be placed. There is a blank border at the top and another on the left side. At the top of each vertical column of holes is placed a card holder. This is made of light tin turned up on the long edges--which are vertical--and tacked to the board. Opposite each horizontal row of holes is a similar tin card holder, but of greater length, and having its length horizontal. The holders at the top of the board contain cards upon which the names of the class are written.
Cards, like the following, are prepared for the horizontal holders.
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Stewart & Gee 229
Physical Manip. 85 Intensity of Gravity--Borda's Method 39
Glazebrook & Shaw 132
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These cards are numbered from one to any desired number and are arranged in the holders consecutively.
Two kinds of nails are provided to fit the holes in the board: An ordinary slate nail and a common picture frame nail with a brass head. The latter indicates work to be done, the former work done.
To prepare the board for service, brass headed nails are placed opposite each experiment, and below the names, care being taken not to have more than one nail in the same horizontal row, unless it is intended that two persons or more are to work upon the same experiment.
There will be no conflict when the brass nails occupy diagonal lines. If they do not, a glance will show the fact.
After an experiment has been performed and a report made upon the usual blank, the brass nail is removed and a slate nail put in its place.
The board will show by the slate nails what work has been done by each student, by the brass nails what is yet to be done, and by the empty holes, experiments which have been omitted or are yet to be assigned. A slate nail opposite an experiment card indicates that that experiment may now be assigned to another person.
It is evident that the schedule for a whole term may be arranged in a few minutes and that the daily changes require very little time.
The board is hung in a convenient place. The student as he enters the laboratory looks for his name on the upper cards and under it for the first brass nail in the vertical column: to the left he finds the experiment card. On the left hand end of the slip he sees the book references, on the right hand end a number--39 in the sample card given above. Knowing the number, he proceeds to a desk and finds a box numbered in the same manner. He removes the box from the closet. On the label of the box is a list of all the apparatus necessary, which he will find in the box; the label also contains the book references. He performs the experiment, fills up a blank which he gives to the instructor, puts all the materials back in the box, replaces the box in its proper place in the closet and proceeds with the next experiment. With this indicator there is no difficulty in managing fifty students or more.
Comparatively little apparatus need be duplicated. Where apparatus is fixed against a wall a number may be tacked upon the wall and a card containing the information desired. The procedure is then the same as with the boxes. The cards on the board being removable, other ones may be inserted containing information in reference to other boxes having the same number but containing different materials. There can be no successful tampering with the board, for the record of experiments performed is upon the blanks which the students turn in and also in the individual note books which are written up and given to the instructor for daily examination.
Lafayette College.
J.W. MOORE.