i9i9« Alexander MacHenry. 103 



set of which had been deposited in the Museum of Practical 

 Geology, London, upon the break-up of Portlock's Survey 

 many years previously. MacHenry devoted all his time 

 which could be spared from field duties to the care of this 

 collection, and kept it in fine order ; one could wander 

 round with a primer or handbook of geology and identify 

 every rock or fossil ! 



In 1877 MacHenry was appointed Assistant Geologist, 

 and the mapping of the wild district of north-west Mayo 

 devolved upon him ; his accurate description of the interest- 

 ing series of granitic and metamorphic rocks can be studied 

 in the Memoir to one-inch sheet 63, etc. Several working 

 seasons he was occupied in endeavouring to trace boundaries 

 in the Devonian series of Cork and Kerry ; later on he joined 

 Glascott Symes in working out the area about his native 

 place, Ballycastle, and he was the first to suggest the shales 

 there being oil-bearing, as well as the probability of the 

 Coal-measures extending under the more recent formations 

 south-westwards and joining in with the Tyrone coalfields, 

 an opinion which recent experiments have so far failed to 

 justify. 



His earlier experience of the supposed similar rocks of 

 N.W. Mayo marked him out to the Director, Prof. Hull, as 

 " the man for Donegal," and at this area he was engaged 

 until the completion of the geological map of Ireland in 

 1889. His mapping of the complex structure of that county 

 has hitherto resisted all crotchet-seekers. In the too short 

 period during w^hich Prof. W. W. Watts was attached to the 

 Irish service MacHenry and he traversed many districts 

 together, investigating the gneissose and felsite rocks of 

 the west of Ireland and unravelling many interesting 

 problems in connection with them, as well as pointing out 

 the occurrence of crush-breccias, hitherto unobserved. 



In 1901, under the direction of Mr. G. W. Lamplugh, 

 MacHenry carried out the survey of the drifts of Dublin 

 City and much of the surrounding country, a work in which 

 his local knowledge afforded him great advantage. During 

 the following three years he pursued similar work in the 

 areas of Belfast, Cork and Limerick, the maps and des- 

 criptive memoirs of which were all rapidly completed and 

 published. 



