264 
ROCK SPECIMENS COLLECTED IN NORWAY. N(>V., 1889. 
wings nearly horizontally after the manner of insects. 
Pigeons often balance for a few seconds in this way, and 
almost all small birds, and the humming bird for much 
longer periods ; but it is, as I have shown, a wasteful action, 
and it would be impossible but for the power, which all 
animals have, of exerting for a few moments an amount of 
energy many times greater than that which they can continue 
to exert for several consecutive hours. It is known that a 
man can exert, for a minute at least, ten times the average 
energy per minute of his day’s work, and it is probable that 
a pigeon balancing in still air is doing much the same. But 
the larger birds, with even smaller wing-surface in proportion 
to their weight, are not able to do this even for a few 
moments; they can support themselves only by moving 
forwards through the air, and when they want to remain in 
the same place they can only do it by flying slowly against 
the wind, so that the wind carries them back as fast as they 
fly forwards, or, if there is no wind, by flying round and 
round in circles. Such birds, when there is no wind, cannot 
rise from the ground until they have acquired some forward 
velocity by running, and the albatross, whose wing-surface 
is only half as great in proportion to its weight as the pigeon’s, 
cannot even acquire sufficient velocity in this way, and, except 
m a wind, cannot rise from the ground at all. 
This subject, the relation of wing-surface to powers of 
flight, is itself a very extensive one, and it cannot be dealt 
with, even in the most elementary way, without mathematics, 
so in this paper I have assumed, without proving, that large 
animals have a smaller wing surface in proportion to their 
weight than small animals, and that this smaller wing surface 
is a disadvantage from the point of view of economy of work 
in flight. 
NOTES ON SOME BOCK SPECIMENS COLLECTED 
IN NOBWAY BY MB. C. PUMPHBEY.* 
BY MR. T. H. WALLER, B.A., B.SC. 
The collection of rocks which Mr. Pumplirey has put 
into my hands for examination and description consists of a 
considerable number of specimens from various localities 
visited by Mr. Marshall and himself between Bergen and 
the North Cape. 
* Transactions of the Birmingham Natural History and Micro¬ 
scopical Society, read 16th October, 1888. 
