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.

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NEW METHOD OF EXTINGUISHING FIRES

This is by George Dickson, of Toronto, Canada, and David Alanson Jones.

A mixture of water and liquefied carbon dioxide upon being discharged through pipes at high pressure causes the rapid expansion of the gas and converts the mixture into spray more or less frozen, and portions of the liquid carbon dioxide are frozen, owing to its rapid expansion, and are thus thrown upon the fire in a solid state, where said frozen carbon dioxide in its further expansion not only acts to put out the fire, but cools the surface upon which it falls, and thus tends to prevent reignition.

A represents a receptacle sufficiently strong to stand a pressure of not less than a thousand pounds to the square inch.

B B water receptacles.