402 
The Geology and Physical Aspect 
bers in column 4, or the values of B—A ; then the numbers in column 
5 will be respectively— 
+ © + ©' 
- — X 
2 
X 4- X' 
— -- + © / 
2 
©' + ©" 
+ - X' 
2 
X' + X" 
-+ ©" 
2 &c., &c., and so on, the algebraic 
signs being carefully attended to: thus in column 5, the first result— 
17.0 + 16.5 
22.65 = 4-p 5.9 
2 
5.9 + 5.7 
22.30 = 4--1- 16.5 &c., &c. 
2 
and from the above observation it would appear, that at lb. 56m. 
on April 6th, 1844, at Van Diemen’s Land, the intensity of 
solar radiation was = 22.51 in scale divisions of the instrument 
employed, which, multiplied into 6.307 (the number of actines 
corresponding to one division of the scale of the instrument), 
would give 141.97 expressed in actines, as the intensity of solar 
radiation at that time of day, and at that period of the year, in 
Tasmania. 
It will therefore be readily perceived, in what a simple manner 
such useful observations can be made, and how comparative they 
become, with the same species of observation made in other parts 
of the globe. In this manner, Sir John Herschel, during his 
residence at the Cape of Good Hope, ascertained by repeated ob¬ 
servations that the intensity of the solar radiation there, as com¬ 
pared with England, was as 48.75 to 27. 
Art. XIX. Observations on the Geology and Physical Aspect 
of the District of Port Phillip , New South Wales; made 
during several excursions from Melbourne to the interior, 
chiefly over the northern and western parts of the country. 
By William Westgartii, Esq. 
General Remarks ,—A large portion of the superficies of the Port 
