Bz PROCEEDINGS OF SECTION a. 
errors of observation, and suggests that, durimg the interval 
between 1863 ard 1881, the declination passed through a 
maximum value, and was in 188] proceeding towards) = 
minimum. This view is borne out by the knowledge that 
in the 15 years preced'ag i881 the dechuation was de 
creasing in the neighbcurmp Stete cf Victoria at an average 
rate of 2! a year. : 
The magnetic survey described in this paper was made 
possible by the grant by the Government of the State of the 
sum of £150 to defray necessary expenses, and by the loan 
by the University of Svdney, through the kind offices of Pro- 
fessor, Pollock, of ee jietmumenis of the usuai type as 
described in Stewart and Gee’s Practical Physics. 
The stations BeAda: ‘were eleven in number, viz., Sca- 
mander, Springfield (near Scottsdale), Longford, Latrobe, 
Cirenlar Head, Strahan, Port Davey, Sorell, Eaglehawk 
Neck, Oatlands, and Southport. They were chosen so as to 
be well spaced over the Isiand, aud at the same time aveid 
the greensione or other igneous rock known or suspected 
to be magnetic. 
Ail the stations enumerated, Seat Port Davey and 
Been ee had heen previously visited by one of the wniters. 
As to the geological fitness of the Port Davey site, there 
cam be no doubt; thd anomalous resulis obtained at South- 
port, to which further reference will be made, are possibly 
due to the proximity of a dyke of magnetic rock not out- 
cropping at ils surface, Tt may here be mentioned that the 
greenstone (ciabase) which covers so large a part of the 
eastern half of Tasran uia ig } highly. Tage etic : 
A reference may here be made ¢o the reasons why we 
did not select Hobart as a site of chservatiou. Tt is obvious 
that, for = of comparison with previous magnetic 
records; a series of observations made at “Bobart would be 
of great value; but, unfortunately, the Domain site employed: 
by Lieutenant Kay is, from a geological point of view, by no 
means a ge one. The magnetic greenstone outcrops ip 
the Domain at no great, distance from the site, and it is by nc 
meazs pate ible thac dykes of greenstone may penetrate 
the Domain sandstones in close proximity to o Kay’s site. It 
is known that Dr. Neumayer, though he set his inetrnmnents 
up in the Domain, did not employ Kay's site; this may 
account In some measure for the result eatated by him. 
Other defects in Kay's site are the proximity of iron roofing 
and pipes placed im position since Kay’s iime. The greatest 
‘defect of all, however, is the disturbing influence introduced 
by the electric trams of ‘Hobart: We were, therefore, re 
luctantly compelied to abandon the Domain as a magnetic 
