Whoever carries a mental kodak with him (as I suspect I was in the habit of doing long before I knew it) must be aware of the uncertain value of the different exposures. This can be determined only by the process of developing, which requires a dark room and other apparatus not always at hand; and so much depends upon the process that it might be well if it could always be left to some one who makes a specialty of it, as in the case of the real amateur photographer. Then one's faulty impressions might be so treated as to yield a pictorial result of interest, or frankly thrown away if they showed hopeless to the instructed eye. Otherwise, one must do one's own developing, and trust the result, whatever it is, to the imaginative kindness of the reader, who will surely, if he is the right sort of reader, be able to sharpen the blurred details, to soften the harsh lights, and blend the shadows in a subordination giving due relief to the best meaning of the print. This is what I fancy myself to be doing now, and if any one shall say that my little pictures are superficial, I shall not be able to gainsay him. I can only answer that most pictures represent the surfaces of things; but at the same time I can fully share the disappointment of those who would prefer some such result as the employment of the Roentgen rays would have given, if applied to certain aspects of the London world. Of a world so vast, only small parts can be known to a life-long dweller. To the sojourner scarcely more will vouchsafe itself than to the passing stranger, and it is chiefly to home-keeping folk who have never broken their ignorance of London that one can venture to speak with confidence from the cumulative misgiving which seems to sum the impressions of many sojourns of differing lengths and dates. One could have used the authority of a profound observer after the first few days in 1861 and 1865, but the experience of weeks stretching to months in 1882 and 1883, clouded rather than cleared the air through which one earliest saw one's London; and the successive pauses in 1894 and 1897, with the longest and latest stays in 1904, have but served to confirm one in the diffident inconclusion on all important points to which I hope the pages following will bear witness.