Jour. sa. Coll.. Vcl, XXXVII.. Art. 0. PI. I. 



iy^t 3 - V .!'< 



Night rcTOi-a on a craiiparatively i-aliii da,y, witli diavactimsticlmif; waves in midiiiglit aiul slirat wavfB in Ihc njnvniiif;. April 3-4, lftI3. (Keiluccd to | original size). 

 T. Tera<la. On Rapid Periodic Variations of T( rrestrial Magnetism. 



