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 maladjustment of his apparatus. But it was not so. He discovered that the nebula he was looking at, as well as many other objects of the same class, was not a mere distant cluster of stars, but that they were masses of glowing gas.

The action of the prism on light from a star is utterly different from its action on the light emitted from glowing gas. In the former case the light is spread out into the long band displaying the rainbow hues if bright enough; in the latter case the light is condensed into one or more luminous lines. The light from the gaseous nebula is exhibited by the spectroscope in a number of bright lines instead of being spread out over the entire length of the spectrum. That nothing should be wanting to complete this splendid contribution to our knowledge of the universe Sir William Huggins discovered the nature of the gases which glow in these faint bluish nebulæ. Even at this early period he succeeded in establishing the existence of hydrogen in these remote regions of space.

The important discoveries we have named may be said to have initiated the application of spectroscopic research to the sidereal heavens. The address that Huggins delivered at Cardiff presents a splendid picture of the harvest of discoveries by this time accumulated. It is natural that so attractive a field of research should have engaged the co-operation of many zealous explorers. To their labours the address rendered ample justice.

At the present moment the attention of the astronomical world is especially directed towards the development of the resources of photography in the various applications which it has to their art. Already the camera has become