The many requests for information regarding the proper height of a single slant light and how to determine what this height should be for lights of various degrees slant, and for operating rooms of various widths, leads us to print the accompanying diagram and explanation of same, which we believe to be a good working basis for building a light that will cover a group extending across the entire width of the room.

The lines at the right of the diagram, beginning 2 ft. 6 in. from the floor, represent lights of 75, 70, 65 and 60 degrees slant, the supposition being that the 70 degree slant, represented by a solid line, is the slant most generally used. At the left of the diagram, from a point 5 ft. high on the wall, a line is drawn at an angle of 45 degrees, representing the light from the extreme top of the skylight, which should fall at a point at least 5 ft. high on this wall, if the extreme end of a large group is to be properly lighted.

The point where this line intercepts the 70 degree angle of the light is 19 ft. from the floor, as shown by the perpendicular line, so it follows that a 70 degree slant light should be 19 ft. high to give proper illumination the entire width of a 20 ft. operating room.

By following the dotted line of 45 degrees from any of the width rooms indicated in the diagram, the point where it touches the 70 degree angle indicates the proper height of the skylight for that width operating room.

By using the scale at bottom of the diagram, the height of any of the other slants given may be readily determined. The long dimension of the light itself is found by measuring from the point where the light begins, to its highest point from the floor. In the case of the light which is 19 ft. high, the length of the light itself is approximately 17 ft. 8 in., and the proportionate width may be determined by the second diagram, which is drawn with the idea of showing the dimensions of any light in the same proportions as the 10 x 12. To find the width when the height is known, follow the straight line from the number on the left indicating the height in feet, to the diagonal line, and from this line to the rule at bottom, the point where the line touches the bottom rule being the proportionate width. As will be seen by the diagram, the light measuring 17 ft. 8 in. the long way should be about 14 ft. 10 in. wide. Diagram No. l.

As in the matter of determining the proper angle for the slant of the light, it must be understood that these rules are not fixed, but are offered as suggestions that we feel are worth following. Diagram No. 2. From An Artura Iris Print By C. L. Venard.

Lincoln. III.