E. Loomis—Barometrie Gradient in great storms. 451 
dient. If we multiply the gradients computed for an area of 
low pressure by 1: 45, we obtain the first six numbers in 
column eleventh of table II; and if we multiply the gradients 
computed for a high area by 1°63 we obtain the last four num- 
bers in column eleventh. We perceive that the differences be- 
tween the numbers in columns G and G@’”” are less than they 
were in table I. 
his comparison indicates that the resistance encountered by 
the air, even over the ocean, is considerably greater than that 
assumed in the formula. Having discovered that the coéffi- 
cient sec. 2, employed in Ferrel’s formula, does not adequately 
represent the resistance which the air near the earth’s surface 
experiences in violent storms, I endeavored to modify the 
ormula so as to represent the observations more accurately, 
and found that the following formula 
a) 
"157 uv sin. p + 1076°4 dirk ath 
ks r (2) 
(i + -004 2) aS 
gave very good results when combined with a suitable coéffi- 
cient. Column fourteenth in table I, shows the numbers com- 
uted from this formula, the last six numbers being obtained 
while in the former case it is on y : 
Applying the same formula to table II, we obtain the num- 
bers in column twelfth; and if we multiply the first six num- 
bers by 2-218 and the last four numbers by 2°362, we obtain 
the numbers in column thirteenth, and we perceive that these 
numbers accord very well with the observed gradients given in 
column third. For both table I and table II, the average error 
of formula (1) (disregarding the algebraic signs) is 0°088™", 
while the average error of formula (2), is only 0-041™". 
_ It may be thought desirable to ascertain how far the preced- 
ing formulas will represent the phenomena of a particular 
storm. For this purpose I have selected the remarkable storm 
of Feb. 5, 1870, of which an account has been given by Capt. 
Toynbee in No. 18 of the Publications of the English Meteoro- 
logical Council. Besides the observations given in Captain 
Toynbee’s Memoir, I have endeavored to obtain additional ob- 
Servations both for the Atlantic Ocean and the adjacent con- 
tinents. For the Atlantic Ocean I have met with small success, 
