Mr HOPKINS, ON RESEARCHES IN PHYSICAL GEOLOGY. 7 



tained in this paper, though their characters are in general mucii less 

 distinct than those of the plienomena already cited. 



III. Anticlinal and Synclinal Lines. 



When two or more anticlinal lines, with the corresponding synclinal 

 ones, are found in the same geological district* their general directions 

 frequently approximate to parallelism with each otherf. 



IV. Longitudinal Valleys. 



a. Along the flanks of elevated ranges, longitudinal valleys are not 

 unfrequently found running nearly parallel to the general axis of 

 elevation \. 



/3. The partial elevations along the sides of an elevated range have 

 usually these escarpments presented towards the central ridge ||. 



* I mean by a geological district, any tract of country throughout which the phenomena may 

 be regarded as following tlie same laws without discontinuity. 



t If we take two planes coinciding at any proposed point of an anticlinal line with the 

 portions of the surface of a stratified bed on opposite sides of that line, these planes' of 

 stratification will intersect in a straight line not necessarily horizontal; and the direction of 

 the anticlinal line at the proposed point will be determined by the azimuth of a vertical 

 plane drawn through this intersection, or the direction of the intersection of this vertical 

 plane with the horizon. Again, if through the proposed point we draw vertical planes 

 respectively perpendicular to the two planes of sti-atification above mentioned, their respective 

 intersections with them will be the lines of greatest inclination of the strata, and consequently 

 the azimuths of these vertical planes will determine the directions (f the dip The angles 

 between these two latter vertical planes, and the one before mentioned as determining the 

 direction of the anticlinal line, will not generally be equal; they will become so only when 

 the inclination of the planes of stratification on either side of the line is the same • i e the 

 directions of the dip on opposite sides of an anticlinal line at any proposed point 'of* it' will 

 not generally make equal angles with that of the line itself, unless the dip on opposite 

 sides be the same. There is however an exception to this rule, when the direction of the 

 dip on each side of the anticlinal line is perpendicular to it. This will occur when the 

 two planes of stratification first mentioned intersect in a horizontal line. 



X Saussure, Voyages dans les Alpes, Vol. I. Chap. x. 



II Traite de Geognosie, by D'Aubuisson, Vol. I. §.24. p. 82.; and Saussure, Voyage dans 

 les Alpes, Vol. III. Chap. x. This rule is probably very general. 



