8 



scribe. This principle has been actually applied — the principle of least 

 action — by Sir Isaac Newton to discover the path of a ray of light. It 

 will apply, as astronomers and mathematicians are aware, to many other 

 branches of science ; it will apply also, I believe, to the unconscious 

 actions of intelligent animals like ourselves. Some years ago, I had 

 the opportunity of observing an unconscious application of this remark- 

 able principle made by an extremely unintelligent class of old women. 

 These were the oyster-women of the Mumbles Harbour, near Swansea. 

 These poor old creatures carried their baskets down to the oyster-beds 

 empty ; they filled the baskets with oysters, and then they had to carry 

 them to the Mumbles along a road which consisted of two parts ; there 

 was the slippery shingle of the beach where they collected the oysters, 

 and after they left that slippery shingle there was a smooth common. 

 Now, this placed the oyster-women in the same position as the ray of 

 light. The velocity of the light in air and its velocity in water are dif- 

 ferent. The velocity of these poor women in the rough shingle, where 

 they occasionally fell, and their velocity on the smooth road, were, as 

 you may suppose, also different, and the friction different. I saw these 

 poor women, to my great amazement, not going from point A to point 

 B as I should have done, nor going perpendicularly so as to get from 

 the shingle in the shortest time on to the common, but making a tack at 

 some point which they seemed to guess at along the line of shingle, and 

 so getting home with less trouble than they would otherwise have done. 

 I had the curiosity to measure the angles made by their path, and made 

 a rough calculation to determine the relative roughnesses of the two 

 roads. I do not suppose that these poor women had any more con- 

 sciousness of what they were doing than the ray of light or the planet 

 has ; they were describing a path of minimum trouble. I can hardly 

 do them the injustice to say that they were lazy animals, because they 

 were the most industrious, hard-working poor creatures I have ever 

 fallen in with, but they were performing unconsciously and instinctiv^ely 

 a great problem — the problem of doing a given amount of work with 

 a minimum amount of effort ; and I venture to say that they performed 

 that problem as the planet describes its path, not by their own intelli- 

 gence, but by the intelligence of Him who made them both. 



I shall take yet another example from organic nature before pro- 

 ceeding to the subject of muscular action. I will take the well- 

 known problem of the cells of bees. Every one knows that the cells of 

 bees are constructed in hexagons, and that the ends of these cells are 

 terminated by the faces of a rhombic dodecahedron. That was the 

 solid so greatly admired by Plato, that he considered it was worthy of 

 representing the earth itself. The tetrahedron represents fire; the 

 octahedron represents air, the cube represents water, but this solid 

 body was reserved in the Platonic system for the' dignity of repre- 



