40 
2. You are required to determine the strength of a current ; 
first, by its action on a magnetic needle ; and, secondly, by its 
electro-chemical action. How would you proceed in the 
respective cases? 
S. A portion of the telegraph wire which unites London and 
Edinburgh, runs magnetically north and south. Supposing you 
had access to the wire while a message was passing, how would 
you ascertain whether the current passed from London to 
Edinburgh, or the reverse ? 
4. Two plates of clean platinum are plunged into acidulated 
water, and a voltaic current is sent through the liquid from plate 
to plate ; how are the plates affected ? Apply your knowledge 
to explain the use of the nitric acid in Grove’s battery. 
5. State the relation which subsists between the length and 
thickness of a wire and the resistance which it offers to the 
passage of an electric current. Describe an experiment which 
shall illustrate the influence of temperature on the conductivity 
of a wire, and state the circumstances on which the heating of a 
wire by an electric current depends. 
6. Sketch an apparatus by means of which y ou could decompose 
water by an electric current ; collect the gases and determine 
their relative quantities. Assuming a direction for the current, 
indicate the place at which the respective gases will appear. 
7. Describe clearly how it is possible to make use of so bad a 
conductor as the earth as a portion of a telegraphic circuit. 
8. Give an account of the origin and laws of induced currents ; 
first, showing how they may be produced by means of a per- 
manent magnet, and afterwards by a voltaic battery. Apply your 
knowledge to explain some one form of the machines used for 
medical purposes. 
John Tyndall. 
EXAMINATIONS IN NATURAL HISTORY. 
In consequence of an alteration in the arrangements of the 
Softool no Students presented themselves for this examination 
in the Session 1860-61. 
Edward Forbes Medal and Prize. 
Morning. 
1. State the distinctive characters of the class Mammalia and 
of its orders. Give examples of each of the latter, and state the 
range of the class in time. 
