Yet children’s observation does not remain at this height of grand selectiveness. The pressure of practical needs tends to bring it down to our familiar level. A child finds himself compelled to distinguish things and name them as others do. The lamb and the dog, for example, have to be distinguished by a _complex_ of marks in which the supremely interesting detail of colour holds a quite subordinate place. Individual things, too, have to be distinguished, if only for the purpose of drawing the line between what is ‘mine’ and ‘not mine’. The boy’s mother, his cup, his hat, must be readily recognised, and this necessity forces the attention to grasp a plurality of marks. Thus the mother cannot always be recognised by her height alone, as when she happens to be sitting, nor by her hair alone, as when she happens to have her hat on, so that the weighty problem of recognising her always compels the child to note a number of distinctive marks, some of which will in every case be available. When once the eye has begun to note differences it makes rapid progress. This is particularly true where the development of a special interest in a group of things leads to a habit of concentration. Thus little boys when the ‘railway interest’ seizes them are apt to be finely observant of the differences between this and that engine and so forth. A boy aged two years and eleven months, after travelling from Dublin to Cork, and thence by another railway, asked his mother if she had noticed the difference in the make of the rails on the two lines. Of course she had not, though she afterwards ascertained that there was a slight difference which the boy’s keener eye had detected. The fineness of a child’s distinguishing observation is well illustrated in his recognition of small drawings and photographs, as when a child of two will pick out the likeness of his father from a small _carte de visite_ group. But this side of children’s recognition will occupy us later on.