Platen. Duiffrain .shemuii tJie Avercuje Mean ihdlv /tre.f.sufr vf tin- (itntospherx- (it Elackhcath 

 utthe hei'qht of 150 ft ahove tlie, level of The .sen-; from Octvber 1,1881 to MajSl, 1882. 



