Hence he may not have thought of the effect of the vertical exposure of a large plate.
In America this is a subject of no little importance.

When an impression is to be developed upon a plate fifteen by seventeen inches, were we to use an angle of about 45 deg., it would be found to make a perceptible difference in the appearance of the image.

By examining the wood tops of our baths as formerly made, it will be found that there is a great variation in the distance from the mercury to the different portions of the plate.

By measuring one of these tops for the size plate above mentioned, I find the distance to the nearest point between the mercury and the plate, to be thirteen, and the middle point sixteen, and the furthest point twenty-one and a half inches: by this we see that one point of the plate is eight and a half inches further from the mercury than the nearest point; even this is not the variation there would necessarily be, were we to adopt the angle of 45 deg.

as urged by Daguerre.
Among our principal professors, the bevel top will not be found in use where the large plates are used.