Those who would wish to have a little extra shop window attraction by way of displaying slides for the season now at hand might do worse than resort to something of the following style. The appliance can hold any number of slides, according to the diameter of the wheel portion, but in the diagram herewith it is for holding a dozen. The slides can be changed readily, hence a little time would be expended in making a complete change at least once a day. [Illustration: FRONT ELEVATION.] The relative portions of the sketch being to scale, particulars as to the making of the revolving wheel need not be entered into, as any mechanic could grasp the whole idea at a glance. The edge of the wheel should, of course, be placed facing the window, and a band on the pulley wheel, A, attached to a clockwork or electric motor would supply all the driving power necessary. In order to get good illumination on the slides, it will be necessary to have a piece of white cardboard or opal glass, B, hung on the axle, the lower side being the heavier, so that although the wheel revolves, it will remain stationary. Various devices may be resorted to for hanging the slides on the cross rods, but perhaps the method shown at C will prove as simple as any, and consists of small springs which grip the slide at both sides. [Illustration: SIDE ELEVATION.] By the judicious arrangement of shielded lights placed at side of reflector, a pretty effect is produced as each slide is gradually brought to view.--The Optical Magic Lantern Journal and Photographic Enlarger. * * * * * THE FECULOMETER. The selling price of beets naturally depends upon their yield in sugar, and what gives potatoes their value is their yield in fecula or starch, a product that serves to nourish man and animals and that is also used in the manufacture of alcohol and glucose. No account, however, is taken of this important coefficient in business transactions, potatoes containing proportions of starch varying from 13 to 23 per cent. being sold at the same price. Nevertheless, it is of the greatest interest to cultivators to make such measurements, since, in order to increase the value of their product, they might thereby be led to make a judicious selection in their planting. [Illustration: THE FECULOMETER.]