Various structural features may be well displayed on separate maps. The trend of the axes of folds will be useful, and may be accompanied by other information of cognate character[25]; maps of the distribution of joint planes may be given in combination with those showing the folding of the strata if it be desired to exhibit the relationship between these; or with the physical features of the country, if the dependence of physical features upon joint structure be under consideration[26]. Much information concerning cleavage may be acquired from a map showing anticlinal and synclinal axes of cleavage[27], or the actual strike of the cleavage over different parts of a map may be represented, and its relationship to the geological structure of the district exhibited[28]. [Footnote 25: See Bertrand, M., "Sur le Raccordement des Bassins Houillers du nord de la France et du sud de l'Angleterre," _Annales des Mines_, Jan. 1893, Plate 1.] [Footnote 26: See Daubrée, A., _Études Synthétiques de Géologie Expérimentale_, 1^{ère} Partie, Plates III.-VI., for an example of the latter, which is also interesting as showing the utility of a map on transparent paper super-posed on another, when illustrating the connexion between two sets of structures.] [Footnote 27: Ward, J. C., _Geology of the Northern Part of the English Lake District_, Plate IX.] [Footnote 28: Harker, Alfred, "The Bala Volcanic Series of Caernarvonshire" (_Sedgwick Essay_ for 1888), Fig. 5.] Maps exhibiting changes in physical geography appertain to the geologist as well as to the geographer. The position of ancient beaches, former lakes, representation of the changes in the courses of rivers and kindred phenomena may be shown upon maps, and will prove useful[29]. [Footnote 29: For examples of maps of this kind, see Kjerulf, Th., _Die Geologie des südlichen und mittleren Norwegen_.] A perusal of the maps to which reference has been made above will give the student some notion of the extent to which maps may be utilised to represent geological structures, and may suggest other methods by which they may be utilised.