166 Mr. R. Griffith onMr. Weaver's Paper relative 



south of the conglomerate of the valley of the Suire and east of 

 that of the Monavoullagh mountains ; while the conglomerate 

 of these mountains rests unconformably on the slate strata to 

 the north and east, and dipping to the southward, forms the 

 substratum or base of the whole of the arenaceous, quartzose 

 and schistose strata to the southward ; and consequently, as 

 these conglomerate beds are admitted by Mr. Weaver to 

 belong to the old red sandstone series, the strata which rest 

 upon them cannot belong to the transition class. I am also 

 decidedly of opinion that the limestones of the valleys of the 

 Suire, the Blackwater, the Bride, and the Lee, all occur 

 in the same geological position, being placed on the top of the 

 series, and that as the limestone of the valleys of the Suire 

 and Blackwater are admitted by Mr. Weaver to be carboni- 

 ferous, all the others must likewise belong to the same series. 



In proof of the accuracy of these views, I formed with 

 great care a section passing through this district nearly in a 

 north and south direction ; and if this section exhibits a cor- 

 rect representation of the relative positions of the several 

 rocks, Mr. Weaver's views must be erroneous. 



This section was exhibited at Newcastle in 1838; at the 

 Geological Society of London, in May, 1839, in illustration 

 of my paper ; and subsequently at the Geological Society of 

 Dublin, in June, 1839, and has since been published in the 

 Journal of that Society. 



I shall now proceed to consider Mr. Weaver's objections 

 to my sections, both as to the principle of their construction 

 and their accuracy. 



He objects to the principle of making the scale of the height 

 much greater than the scale of length, as he observes that 

 " without considerable labour it leads to inaccuracy, as such 

 sections, unless done correctly, instead of conveying precise in- 

 formation, tend rather to mislead the judgement." I quite 

 agree to the position that an inaccurate section will tend to 

 mislead ; but if a section be made with care, and the relative 

 positions of the rocks be accurately laid down according to 

 the respective scales, no error can arise, though the angle of 

 the dips will be necessarily increased. 



The direct advantage to be derived from making the scale 

 of height greater than the scale of length is, that supposing 

 the scale of 8 to 1 be taken, the length of the paper on which 

 the work is laid down is but £th of the length which it would 

 be, if equal scales of length and height were adopted ; and in 

 long sections this is most important, by bringing the whole 

 subject under the eye at one time, instead, as must otherwise 

 be the case, of having it in a long roll, or different portions 





