THERE are unregistered as well “registered” thieves. How many of the former make London their hunting-ground, it were much more difficult to enumerate. Nor is it so much out of place as might at first appear, to class both phases of rascality under one general heading. We have to consider the sources from which are derived our army of London thieves. It is not as though the plague of them that afflicts was like other plagues, and showed itself mild or virulent, according to well-defined and ascertained provocatives. On the contrary, the crop of our crime-fields is even more undeviating than our wheat or barley crops. A grain of corn cast into the ground may fail, but the seeds of vice implanted in kindly soil is bound to germinate, unless the nature of the soil itself is altered. As already stated, the number of our London thieves has somewhat decreased of late years, but it is merely to the extent of six or seven per cent. If it is twenty thousand at the present time, this day twelvemonths, allowing for the increased population, it will be nineteen thousand, say. Appalling as are the criminal returns for the city of London, it would be a vain delusion to imagine that when the “twenty thousand” have passed in review before us, the whole of the hideous picture has been revealed. The Government statistics deal only with “professional criminals;” that class of persons, that is to say, who have abandoned all idea of living honestly, and who, weighing the probable consequences, resign themselves to a life of systematic depredation, and study existing facilities, and likely new inventions, just as the ingenious joiner or engineer does in an honest way.