Types, diameters, and total visual magnitudes are thus available for some 400 of the nebulae in Holetschek’s list. The few unclassified objects are all fainter than 12.5 mag. The data are listed in Tables I–IV, in which the N.G.C. numbers, the total magnitudes, and the logarithms of the maximum diameters in minutes of arc are given for each type separately. A summary is given in Table V, in which the relative frequencies and the mean magnitudes of the various types will be found. RELATIVE LUMINOSITIES OF THE VARIOUS TYPES The frequency distribution of magnitudes for all types together and for the elliptical nebulae and the spirals separately is shown in Table VI and Figure 1. With the exception of the two outstanding spirals, M 31 and M 33, the apparent luminosities are about uniformly distributed among the different types. The relative numbers of the elliptical nebulae as compared with the spirals decrease somewhat with decreasing luminosity, but this is very probably an effect of selection. The elliptical nebulae are more compact than the spirals and become more stellar with decreasing luminosity. For this reason some of the fainter nebulae are missed when small-scale instruments are used, although the same luminosity spread over a larger area would still be easily detected. The effect is very pronounced on photographic plates. It accounts also for the slightly brighter mean magnitude of the elliptical nebulae as compared with the spirals in Table V. TABLE I Elliptical Nebulae ==========+===========+======== N.G.C. | m_{T} | log d ----------+-----------+-------- E0 (17) ----------+-----------+-------- 404 | 11.1 | +0.11 474 | 12.6 | – .40 1407 | 10.9 | .15 3348 | 11.8 | – .15 3379* | 9.4 | + .30 4283 | 12.2 | – .52 4486* | 9.7 | + .30 4494* | 10.1 | – .15 4552* | 9.9 | + .23 4589 | 11.4 | – .30 4648 | 12.3 | .52 5044 | 11.8 | .30 5216 | 13.3 | .70 5273 | 12.1 | .52 5557 | 12.3 | .40 5812 | 12.0 | – .40 5846 | 10.9 | 0.0 |-----------|--------- Mean | 11.40 | –0.204 ----------+-----------+--------- E1 (13) ----------+-----------+--------- 467 | 13.0 | –0.70 596 | 11.8 | .22 1400 | 11.1 | .22 2880 | 12.0 | .52 3226 | 12.0 | .10 3962 | 11.8 | – .30 4278* | 10.8 | .0 4374* | 9.9 | + .08 4472 | 8.8 | + .30 4478 | 11.5 | – .10 4636 | 10.9 | + .08 5813 | 12.6 | – .30 7626 | 12.3 | –0.30 ----------+-----------+--------- Mean | 11.43 | –0.177 ----------+-----------+---------