As a sunshine recorder, the instrument gives a perfect record, in which the varying intensities are readily recognizable. Since the cylinder moves one-half inch in an hour, and the slit is .01 of an inch, the time of each exposure is 72 seconds. This gives a very deep color on the solio paper, which results in a serious error in making comparisons with the standard. On account of the hood, diffuse light is not recorded when it is too weak to cast a distinct shadow. It seems probable that this difficulty will be overcome by the use of a flat disk containing the proper slit, and in this event the instrument will become of especial value for measuring the diffuse light of layered formations. The celluloid sheet constitutes a source of error in sunlight on account of the reflection which it causes. This can be prevented by using the instrument only on sunny days, when the protection of the sheet can be dispensed with. =81. The selagraph.= This instrument is at present under construction, and can only be described in a general way. In principle it is a simple photometer operating automatically. It consists of a light-tight box preferably of metal, which contains an eight-day lever clock. Attached to the arbor of the latter is a disk 7 inches in diameter bearing on its circumference a solio strip 1 cm. wide and 59 cm. long. The opening in the box for exposure is 6 mm. square and is controlled by a photographic shutter. The latter is constructed so that it may be set for 5, 10, or 20 seconds, since a single period of exposure can not serve for both sun and shade. The shutter is tripped once every two hours, by means of a special wheel revolving once a day. Each exposure is 6 mm. square, and is separated by a small space from the next one. Twelve exposures are made every 24 hours, and 84 during the week, though, naturally, the daytime exposures alone are recorded. Comparisons with the multiple standard are made exactly as in the case of the simple photometer. The selagraph is made by the C. H. Stoelting Co., Chicago, Illinois. _Standards_