334 Correspondence — Mr. L. C. Miall. 



on the otlier hand from the present position of the plane to calculate 

 its original dip. 



1st. rind by problem 1 the dip of the plane in the direction (a) of 

 the secondary tilt and (b) of its strike. 



2nd. Add or subtract (as the case may require) to or from (ct) the 

 amount of the secondary tilt (n). 



3rd. From a + n and h (two apparent angles) find the full dip and 

 its direction by Problem 2. 



Example. — A plane dips N. at 50°, and is subsequently tilted 49° 

 to W. 30° S. Find its final position. Its original dip to W. 30° S. 

 by Prob. 1, is by diagram — 30|°, by logarithms — 30° 47' (being 

 that amount to E. 30° N.) and to N. 30° W., 45|° (logs. 45° 54'). 



After the secondary tilt the dips are W. 30° S. 181° (49_30|) and 

 N. 30 W. 45f . 



The resultant position being 47° to W. 42° N. or by logs. 47° 17^ 

 to W. 42° 19' N. 



W. H. Dalton, H.M. Geol. Survey. 



LABYRINTHODONTS OF THE COAL-MEASUEES. 



Sir, — At the last meeting of the British Association, in August, 

 1872, the following resolution was adopted : 



" That Professor Phillips, Professor Harkness, Mr. Henry Wood- 

 ward, Mr. James Thomson, and Mr. L. C Miall be a Committee 

 for the purpose of investigating and reporting upon the Laby- 

 rinthodonts of the Coal-measures; and that Mr. L. C. Miall be the 

 Secretary." 



The Committee has entered upon its work, and it is hoped that 

 useful results will be laid before the Association from time to time. 

 It has become clear that the preliminary investigation at least must 

 not be limited to British Carboniferous Labyrinthodonts, but must 

 include the Triassic genera as well as the Carboniferous examples 

 discovered in other countries. The successful prosecution of the 

 inquiry is therefore found to depend in part upon the assistance 

 which can be rendered by geologists resident in different parts of 

 the world. 



I am instructed by the Committee to inquire whether you can aid 

 us in any way. Casts and photographs of instructive specimens, 

 drawings, if practicable, of full size, and measurements of such 

 parts as can be clearly identified, would be specially valuable. The 

 Committee will further be glad to receive any publications bearing 

 on the subject, which may not be readily accessible in England. 



^ LEBD^5f«y^?7^' ^- C- ^^^^^' ^^'''•^^^'-y ^^ ^^^ committee. 



