The difficulties in the way of authentication are by no means slight, but space will not allow me to dwell upon them; the most ready means, however, is that of watching the old bird to the nest, although even in this, as the collector will find by experience, there is a certain liability to error. In collecting abroad it will be found absolutely necessary (however reluctant we may be to sacrifice life) to procure one of the parents with the nest and eggs. As we are writing for beginners at home, we trust such a measure will rarely be necessary; but that an accurate knowledge of the appearance of the bird, its nesting habits, the situation, and the materials of which the nest is composed, will be found amply sufficient to identify the eggs of our familiar birds. This knowledge of course is only to be obtained by patient and long observation; but it is just by such means that the student obtains the practical insight into the habits and peculiarities of the objects of his study, together with the careful and exact method of recording his observations, which eventually enables him to take his place amongst the more severely scientific naturalists whom he desires to emulate. I will first describe the tools required, and then proceed to the mode of using them. [Illustration: Fig. 4. Fig. 5. Drills for perforating Birds' Eggs.] Figs. 4 and 5 are drills used for making the hole in the side of the egg, from which the contents are discharged by means of the blowpipe, Fig. 6. Fig. 4 has a steel point, brass ferrule, and ebony handle, and may be used for eggs up to the size of the wood-pigeon's; Fig. 5 is all steel, the handle octagonal, to give a firm hold to the fingers in turning it, and may be used for eggs from the size of the wood-pigeon's upwards. The points of both are finely cut like the teeth of a file, as shown in the woodcut. The blowpipe, Fig. 6, is about 5-1/2 inches in length (measured along the curve), and is made of German silver, which from its cleanliness, lightness, and freedom from corrosion, will be found the most suitable: it should be light and tapering, and with a ring at the upper end to prevent it from slipping out of the mouth when used. A piece of thin wire, Fig. 7, should be kept in the tube when not in use, to prevent it from becoming stopped up by any foreign substance. A common jeweller's blowpipe may be used for large eggs, such as those of gulls and ducks. Fig. 8 is a small glass bulb-tube, which may be used for sucking out the contents of very delicate eggs, and other purposes, which will be explained hereafter. The small drill and blowpipe may be carried inside the cover of the note-books. [Illustration: Fig. 6. German-silver Blowpipe.] [Illustration: Fig. 7. Wire for unstopping ditto.] [Illustration: Fig. 8. Glass Bulb-tube, for sucking eggs.]