322 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vo.. VIII. 
2. The second principle is that of floating on account of equal specific 
gravity with the medium.. This principle, which nature employs chiefly 
for animals in the water, man has adopted in the balloon. 
3. The third method is the employment of a very rapid movement 
of a character not perfectly explained yet. We see this principle in 
the flying apparatus of the insect. It is obviously applicable only in 
case of comparatively small creatures. 
4. The fourth principle is that applied in the birds, bats, and other 
flying animals. The suspension in the air is obtained partly by down= 
ward pressure, and partly by the kite-like gliding movement of the wings, 
the surface of the latter being immensely enlarged by the feather system. 
The above mentioned relations between surface and gravity, deter- 
mine the limit of size for flying creatures on the surface of this earth. 
Nature has not succeeded in producing flying birds above a certain 
weight. Theextinct Moa were very large birds, but they could not fly, 
nor can the cassowary and ostrich. They are too heavy. Nature, using the 
above mentioned principles, could not produce wings which would carry 
a larger body and a larger brain, and since the latter, i. e., the increase 
of brain was indispensable to further development, it had to give up flying 
as the chief way of locomotion for its highest creatures, and was compelled 
to branch off from a lower order again, laying all stress on the evolution 
of brains. Thus the mammals arose which are bound to the earth. 
And to the brain development of the highest species of mammals i. e., 
man, it is left to find another (fifth) method to suspend a body in mid-air, 
a method which will not fail in the case of greater weights. For with the 
application of the fish (balloon) and the bird method, one will scarcely 
get much further than Nature. 
Let us see now what would happen if that twenty times enlarged animal 
and the surface of the earth would also be removed to twenty times greater 
distance from the centre. The weight of the animal which was twenty 
times too great for its muscle power would have to be now multiplied 
by 203 on account of the increased mass of the earth, and divided by 
207 on account of its greater distance from the centre, thus it would have ~ 
oo. times, i. e.—twenty times the weight of the original animal, but as 
it is twenty times as strong the two influences just cancel one another. 
3. SPACE HAS IN FIRST LINE A QUALITATIVE CHARACTER. 
When experimental psychology saw the light of the world as a new 
science, there happened, what in fairy tales so often takes place at the birth 
ea 
