direct scrutiny. On withdrawing the eye to another part of the field, however, the mystery is solved. If the object is a nebula, it flashes very distinctly on the retina; but if a small cluster, the individual stars are seen sparkling in it. These indirect views are usually so effective that the trouble of applying higher powers is dispensed with. The glow from a faint nebula or comet often apparently fluctuates in a remarkable manner. Light-pulsations affect it, causing the nebulosity to be intermittently visible. It flashes out and enlarges, then becomes excessively feeble and indeterminate. The changes are not real, but due to the faint and delicate nature of the object, which is only fugitively glimpsed and presents itself differently with the slightest change in the manner of viewing it. Burnham has said there is no such thing as glimpsing an object; but he is wrong. It is the intermediate step between steady visibility and absolute invisibility. The work of sweeping for nebulæ is much delayed by the comparisons necessary for the identification of objects. The path may be smoothed by marking the known nebulæ on a good chart, like Argelander’s. The observer may then see, by reference, whether the objects he encounters have been picked up before. The labour of projecting all the nebulæ contained in the New General Catalogue would of course be considerable, and the observer will probably find it expedient to select certain regions for examination, and map such nebulæ as are included within their borders. The discovery of new nebulæ offers an inviting field to amateurs. Vast numbers of these objects have escaped previous observation, for though the sky has been swept again and again, its stores have not been nearly exhausted. Mr. Barnard recently stated that with the powers of the great 36-inch refractor the number of known nebulæ (more than 8000) might readily be doubled! As an example of their plentiful distribution in certain regions it may be mentioned that Mr. Burnham very recently discovered eighteen new nebulæ in a small area of 16′ by 5′·5 near the position in R.A. 13^h 38^m, Dec. 56° 20′ N. Near the pole of the northern heavens there exist many unrecorded nebulæ, as this region does not appear to have been thoroughly examined with a large instrument. It is often the case that several nebulæ are clustered near together. Whenever a new one is discovered the surrounding space should therefore be carefully surveyed in search of others. The region immediately outlying known objects may also be regarded as prolific ground for new discoveries. After several hours’ employment in the work of searching for nebulæ or comets the eye is enabled to discern faint objects which were invisible at first, as it is in a better condition to receive feeble impressions. While comet-seeking in 1889 and 1890 I discovered ten new nebulæ, all near the N. pole, and their approximate positions are given below:—