s 
J. M. Safford on the Upper Silurian Beds of Western Tenn 205 
» tx 
H Jan. |Feb. | March} Apr.; May|June July; Aug. | Sept. Oct. | Nov.} Dec. 
Mean declinom, readings,/563* |563°1} 563-5 |562-6/561-1} st 2-2} 562-1|561-2/558-4/558°1 1554 : 
Corr. fur secular change, | -4'4| ~-3:6| —2-8 | ~2-0) -1-2} -0 4; +0-4 +13 +20) +2: 
Annual variation in are, |-+0'-5|+0-4! 0-1 | —0-11 40:2} —0°6} —1-0| -—u°9! 0-0) —0-2/ 46: 
This result has been adopted as representing the annual vari- 
ation. From June to October the north end of the magnet is 
are. It is ref tones that this range at the same station is increas- 
ing, or diminishing, 
Art. XVIII.—The Upper Silurian Beds of Western Tennessee ; and 
Dr. F. Roemer's Monograph; by Prof. J. M. Sarrorp, Leba- 
non, Tenn, — 
valent to 
the Niagara group of New York. This bed I have denc inated 
i ge 
the sponge-bearing bed, the appropriateness of which name is at 
once seen by referring to Dr. r’s eS 
a. Die Silurische Fauna Des Westlichen Ter . Bine Pa gare 
on- 
ographie von Dr. Ferdinand Roemer; Breslau, 1860. See this Journal, xxi, 127. 
Am. Jour. Ce pot gee: Vou. XXXI, No. 92,—Marca, 1861. 
