The methods I would recommend are these: That after the extraction of a stone from the bladder, tho’ the whole of its surface be rough, the operator should nevertheless introduce the forefinger of his left or right hand thro’ the wound into the cavity of the bladder; by which means, if the subject be under twelve years of age, he will be enabled to come in contact with every internal part of the bladder with his finger: but if the subject be an adult, and of a corpulent habit of body, the finger, under these circumstances, not being found to be sufficiently long for the purpose, he must have recourse to a female catheter, or some other instrument that is nearly strait, quite smooth and polished, and of about nine or ten inches long; which will serve the purpose equally well, if of a proper form and thickness. This is the method I have made use of upon the like occasions of late years, without giving any great degree of pain to the patient, or considerably retarding the operation. Since I have had the opportunity of making the following observation, as well as a prior observation something similar to this, where two rough stones were extracted by me a few years ago from a young man’s bladder of 15 years of age, I cannot help suspecting, that there may have been instances of one or more stones being left behind in the bladder at the time of operating, merely from the operator’s putting too great a confidence in this general rule. Which suspicion I am led into from having known people, who have undergone the operation of cutting for the stone, relapse into the like disorder in a short time after the healing of their wounds, attended with such symptoms, as have obliged them to submit to a second operation; when the stone, upon being extracted, has appeared of so considerable a size, as to make it suspicious, that this stone must probably have been of a much longer growth, than the short time betwixt the two operations could admit of. The maxim laid down to us by authors, of a smooth and polished stone in the bladder being never there alone, but always accompanied with one or more stones of the same kind, I know no exception to. But if this phænomenon should ever occur, the strict observance of that rule (delivered to us by judicious writers in surgery) of always searching the bladder under the like appearances, on presumption of one or more stones being left behind, cannot be attended with any future mischief to the patient, when carefully executed by the methods recommended above, and undoubtedly should always be strictly attended to. The smooth and polished appearances of the surfaces of human _calculi_ are universally supposed to arise from their rubbing one against the other; which may with reason be supposed to be the case: but I confess this inference is not satisfactory to me; since it is probable, if this was the sole cause of their smoothness, the same effect would probably be