Being all of wood, it is easily made by any one who can use a few tools, the only bit of lathe work necessary being the turned shoulder, K, of polar axis. A is the baseboard, 9 in. by 5 in., near each corner of which is inserted an ordinary wood screw, S S, for the purpose of leveling the base, to which two side pieces are nailed, having the angle, _x_, equal to the co-latitude of the place. On to these side pieces is fastened another board, on which is marked the hour circle, F. Through this board passes the lower end of the polar axis, having a shoulder turned up on it at K, and is secured by a wooden collar and pin underneath. On to the upper part of the polar axis is fastened the declination circle, C, 5½ in. diameter, made of ¼ in. baywood, having the outer rim of a thin compass card divided into degrees pasted on to it. The hour circle, F, is half of a similar card, with the hours painted underneath, and divided to 20 minutes. G is the hour index. D is a straight wooden pointer, 12 in. long, having a piece of brass tube, E, attached, and a small opening at J, into which is fixed the point of a common pin by which to set the pointer in declination. H is a nut to clamp pointer in position. By this simple toy affair I have often picked up the planet Venus at midday when visible to the naked eye.--_T.R. Clapham in English Mechanic_. [Illustration: A STAR FINDER.] * * * * * The best mode of finding or tracing trichinae in pork by means of a microscope is the following: Cut a very thin longitudinal slice of the muscle by means of a very sharp knife or razor. Press it between two glass slips, and examine by transmitted light, The coiled trichinae may be readily distinguished from the muscle fiber. * * * * * THE SCIENTIFIC AMERICAN SUPPLEMENT. PUBLISHED WEEKLY. TERMS OF SUBSCRIPTION, $5 A YEAR. Sent by mail, postage prepaid, to subscribers in any part of the United States or Canada. Six dollars a year, sent, prepaid, to any foreign country. All the back numbers of THE SUPPLEMENT, from the commencement, January 1, 1876, can be had. Price, 10 cents each. All the back volumes of THE SUPPLEMENT can likewise be supplied. Two volumes are issued yearly. Price of each volume, $2.50, stitched in paper, or $3.50, bound in stiff covers. COMBINED RATES--One copy of SCIENTIFIC AMERICAN and one copy of SCIENTIFIC AMERICAN SUPPLEMENT, one year, postpaid, $7.00. A liberal discount to booksellers, news agents, and canvassers. MUNN & CO., PUBLISHERS, 361 BROADWAY, NEW YORK, N.Y. * * * * * PATENTS. In connection with the SCIENTIFIC AMERICAN, Messrs. MUNN & Co. are Solicitors of American and Foreign Patents, have had 42 years' experience, and now have the largest establishment in the world. Patents are obtained on the best terms.