Page:Philosophical Transactions of the Royal Society A - Volume 184.djvu/10

of cell, 1.7 inches. When light passed through length of cell to the sensitive paper a double sector with an opening of 12° rotated in front of the clear cell. When light passed through the breadth of the cell, the sector opening was 36°.13.

For the cells placed lengthways, the value obtained for the light after passing through the clear cell had to be multiplied 180/12= 15. When the cells were placed breadthways, the value for the light passing through the clear cell had to be multiplied by 180/36.13 = 4.982.

The photographic light passing through the clear water = 1.17 × 15 = 17.55 times that passing through the turbid water.

Using the formula T = Ie""^ log 17*55 = 2-86504 = 3'15/x2 fil= '911 for each inch of turbid water.