These rings bear the name of Newton who in 1672 had created the device in order to observe them and had discovered experimentally that the thicknesses of the layer of air in correspondence to the miscellaneousous rings are proportional to integers.
In the exemplar in this collection, which belongs to the version of Newton's apparatus that was most widely used in the 19th century, the lens and the glass disk on which it lies are held by two sturdy brass frames having a diameter of 8.3 cm, from which they protrude for just over a millimetre in the parts facing each other.
The lens and the disk are held together by three long, equidistant levelling screws arranged around the edge of the frames; they allow miscellaneousation of the distance between them and also act as the feet of the device.
The bottom side of the disk is blackened to avoid the presence of the beam reflected by it.
This device, when illuminated with a beam of monochromatic light, allows observation of the fact that on increasing the distance between the lens and the disk on which it lies by means of the levelling screws holding them together, the clear rings occupy the place of the dark ones, converging towards the centre, and this occurs with every removal by a quarter of the wavelength.