In the case of a reflection grating the same method applies.
In the vertical shaft there is first of all a grating which intercepts solid matters, and then, lower down, a central valve which can be opened and closed at pleasure from the top of the shaft.
Under these circumstances, if the material of the grating be completely transparent, the whole of the light must appear in the direct image, and the ruling is not perceptible.
The metallic plate thus produced formed, when stripped from its support, a reflection grating reproducing many of the characteristics of the original.
He has also shown how to rule a plane surface with lines so disposed that the grating shall of itself give well-focused spectra.
The heavy door opened with a grating sound.
The grating at A and the eye-piece at 0 are rigidly attached to a bar AO, whose ends rest on carriages, moving on rails OQ, AQ at right angles to each other.
Lyman more recently has been able to obtain photographs as far down as 1030 A with the help of a concave grating placed in vacuo.
The directions of the lateral spectra are such that the passage from one element of the grating to the corresponding point of the next implies a retardation of an integral number of wave-lengths.
If, further, on leaving the grating the light be received by a focusing lens, e.g.