230 Geological Survey of Great Britain. 
ceived a complete organisation. At Colonel Colby’s desire 
Captain Portlock then erected a geological and statistical 
office, a national museum for geological and zoological objects, 
and a laboratory for the analysis of minerals. 
In 1840, the plan of continuing the Londonderry Memoir 
was again abandoned, the museum and laboratory transferred 
from Belfast to Dublin, and Captain Portlock instructed to 
collect, ina special work, all the geological data which he 
had collected in the county Derry and the barony of Dun- 
gannon. For this purpose various new investigations were 
set on foot in the neighbouring districts, and in 1843 the 
work was published under the title of Report on the Geology 
of the County of Londonderry, and of parts of l'yrone and Fer- 
managh. This work, in the completion of which Mr Oldham 
materially assisted, contained a general map on the scale of 
half-an-inch to the English mile, whilst the original surveys 
(which, however, were not published) were entered on the 
maps of the Trigonometrical Survey on the scale of six inches 
to the mile. Many geological sections, as well as engravings 
and descriptions of the fossils, accompany the work. 
In the meanwhile, another undertaking had occasioned the 
foundation of the Museum of Economic, or, as it is now called, 
of Practical Geology, in London.* When the erection of the 
new houses of Parliament was determined, it became, in the 
first place, necessary to make a careful selection of the 
most suitable building-stone, in order to give a correspond- 
ing durability to an edifice which was to be carried out with 
a magnificence worthy of the greatness of the English na- 
tion. A special commission was placed under the direction 
of Sir H. De la Béche, which, by the most careful examina- 
tion, supplied the data needed for such a choice. On the one 
hand, they considered the quality of the stone as deducible 
from direct experiments,—such as the chemical composition, 
* The Museum of Practical Geology orginated in Mr Henry De la Béche 
having, during the progress of the Geological Survey, then in Cornwall, in 
1835, represented to the Government the advantages that would arise if that 
survey were made available for collecting objects illustrative of the application 
of geology to the useful purposes of life, so that the requisite information might 
be obtained by those who might be required to direct, or might be anxious to 
promote works, either for the ornament or good of the country. 
