778 REPORT—1890. 
8. The Orthophote. By Jamus T. Brown. 
An instrument for the instant and simultaneous correction of photometric 
observations for consumption of standard, volume of gas, and variations in the: 
amount of gas consumed in the test burner. 
This instrument, as arranged for use, with photometers fitted with graduated 
bars, consists of two similar, appropriately-calculated, logarithmie scales, with 
numbers and marks corresponding with those on the photometer bar. The lower 
scale is at the upper edge of the lower bar, and the upper scale is at the lower edge- 
of the upper bar. These two scales are separated by an interval, in which a slide 
works freely. The lower half of the face of this slide is graduated in terms of the 
unit adopted as standard, and the upper half is occupied by a scale for the correc- 
tion, of the gas consumed, for variations in atmospheric conditions. The normal,. 
or standard lines of these two scales exactly correspond, and as they are engraved 
on the same sliding block they cannot be misplaced with reference to one another. 
Then, by moving the slide so that the number indicating the extent to which the: 
standard has varied from its normal rate of consumption is opposite the bar-reading, 
the position of the normal line on that scale shows what the bar-reading would 
. have been if the standard had consumed its correct quantity. Now, if the atmo- 
spheric conditions have been normal, that will be the corrected value of the gas; 
but if these are abnormal, the finally-corrected reading of the gas-value will be 
opposite the tabular (or Aérorthometer) number. If the standard employed does 
not require correction, the lower half of the slide has no scale. If the reading is 
taken by the quantity of gas required to render a disc evenly illuminated, that gas: 
scale may be either on the lower, long bar, or on the lower half of the slide. The 
instrument can be fitted with the appropriate scales and slide for any photometer, 
any standard, and any range or quality of gas. It may be arranged vertically, or 
with the long scales on a bar sliding in a groove between the two short scales. 
SATURDAY, SHPTEMBER 6. 
The Section did not meet. 
MONDAY, SEPTEMBER 8. 
The following Reports and Papers were read :— 
1. Report of the Committee on an International Standard for the Analysis 
of Iron and Steel—See Reports, p. 262. 
2. Report of the Committee on the Influence of Silicon on the Properties 
of Steel_—See Reports, p. 262. 
3. Report of the Committee on the Properties of Solutions. 
See Reports, p. 310. 
A. Report of the Commitee on the Bibliography of Solution. 
See Reports, p. 310. 
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