Among other objects which served as an unfailing source of amusement, when resting from the fatigue of my walks, was the little inhabitant of the brook which is spoken of in the extract made from the "Journal of a Naturalist," in last week's Friend. These merry swimmers occupied every little sunny pool in the stream, apparently altogether engaged in sport. A circumstance (not adverted to in that extract) connected with these insects, gives them additional interest to a close observer--they are allied by their structure and nature to those nauseous vermin, the cimices, or _bed-bugs_; all of which, whether found infesting fruits or our dormitories, are distinguished by their disgusting odour. But their distant relatives, called by the boys the _water-witches_ and _apple-smellers_, the gyrinus natator above alluded to, has a delightful smell, exactly similar to that of the richest, mellowest apple. This peculiarly pleasant smell frequently causes the idler many unavailing efforts to secure some of these creatures, whose activity in water renders their pursuit very difficult, though by no means so much so as that of some of the long-legged water-spiders, which walk the waters dry-shod, and evade the grasp with surprising ease and celerity. What purposes either of these races serve in the great economy of nature, has not yet been ascertained, and will scarcely be determined until our store of _facts_ is far more extensive than at present. Other and still more remarkable inhabitants of the brook, at the same time, came within my notice, and afforded much gratification in the observation of their habits. The description of these we are obliged to defer for the present, as we have already occupied as much space as can be allowed to our humble sketches. JOHN. No. III.