APPENDICES. 



APPENDIX A. 



OhservatAons for determining Altitudes of Stations in Marocco. 



By John Ball. 



The instruments provided for tlie measuring of heigtts during 

 our journey in Marocco were, in the first place, two mercurial 

 barometers belonging to Sir J. Hooker, which were unfortunately 

 left behind at the last moment by his attendant who had them 

 in charge. Mr. Ball carried an aneroid barometer, by Secr^tan 

 of Paris, which, during many mountain journeys before and 

 since, has performed very satisfactorily ; and Mr. Maw had a 

 small pocket aneroid of ordinary construction, not deserving of 

 much confidence. 



At Sir J. Hooker's request, Mr. Carstensen, then British Vice- 

 consul, and M. Beaumier, French Consul at Mogador, both 

 recorded observations of the barometer and thermometer twice 

 daily (at 10 a.m. and 4 p.m.) during the period of our stay in 

 and near to the range of the Great Atlas. Mr. Carstensen's 

 instrument was a mercurial barometer, apparently a moderately 

 good instrument ; but, inasmuch as it showed itself more 

 sluggish than M. Beaumier's instrument, and the amplitude of 

 its variations was less considerable, its records do not appear to 

 deserve equal confidence. On rendering the measurements into 

 millimetres, and correcting both instruments so as to bring the 

 indications to 0° C. at the sea level, the observations with the 

 mercurial barometer fall short of those of the other instrument 

 by a mean difference of 5-5 mm., the chief cause of the dis- 

 crepancy being apparently due to the scale of the former being 

 unduly low. Comparing corrected observations for ten days 

 of very settled weather, during which the utmost range of either 



