398 Progress in Science. [July, 



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treatise on the motions of the human body, but the work is a less systematic 

 and complete one than that of Borelli. 



The lecturer said that he would explain what he meant by " the Principle of 

 Least Action in Nature," by the aid of a few illustrations. Let the earth be 

 supposed to be a lazy animal swimming round the sun in a curve which would 

 enable it to complete the journey with the least trouble and exertion to itself; 

 on this assumption, if two certain points in the path of the planet be known, 

 also the position of the sun, the whole of its path can be accurately cal- 

 culated and predicted. If a ray of light on striking and being bent from its 

 original path by a piece of glass be supposed to be a living intelligent animal 

 trying to perform its journey through air and glass at the least trouble 

 to itself, on this hypothesis its path can be calculated and predicted, just 

 as easily as by the laws of refraction and reflection. Some time ago he saw 

 some oyster women at the Mumbles Harbour, near Swansea, carrying their 

 oysters along a road which consisted of two parts ; there was the slippery 

 shingle of the beach, and beyond that the smooth common. The velocity of 

 these poor women on the shingle and on the common was different. They did 

 not go straight from the shingle to the common as he would have done, 

 but " made a tack ;" he afterwards measured the angles made by their path, 

 and made a calculation which proved to him that they had unconsciously 

 taken the path of minimum trouble. Lastly, he cited the instance of the cell 

 of the bee, in which the largest quantity of cell-space is obtained with the 

 minimum quantity of wax. 



Dr. Haughton then stated that before proceeding to apply thi3 principle of 

 least action in nature he found it to be necessary to obtain the coefficient of 

 muscular force. What is known to engineers as the coefficient of a rope, 

 means the number of pounds or tons weight necessary to break it across. If 

 a rope of muscle one square inch in cross section were hanging from the roof 

 of the theatre of the Royal Institution, and that muscular rope were acted 

 upon by the will, its coefficient would be the weight it would lift from the 

 ground by contraction. It cost him twelve years of hard work to obtain this 

 coefficient in pounds per square inch for human muscle. He had not succeeded 

 in obtaining it for any other animal but man, the hairy quadrupeds with long 

 tails not being intelligent enough to submit to the necessary experiments. He 

 had determined that 94*7 lbs. per square inch of muscular fibre was the weight 

 which the arms of a young man accustomed to athletic exercises was capable 

 of lifting; 110-4 l° s - was tne coefficient of the muscular fibres of the legs; 

 and 107 lbs. of the muscles covering the abdomen ; consequently 104*04 lbs. 

 was very nearly the coefficient of muscular force. 



He had obtained this information by dint of hard study of cases of cholera, 

 hydrophobia, and lock-jaw in hospitals, in which very painful contortions 

 sometimes occur, but which threw light upon some of the problems in animal 

 mechanics. He had also learnt the secret of working the treadmill in a lazy 

 manner, and could get through the work with the least trouble to himself as 

 well as the most expert burglar in London ; he also knew where to place him- 

 self to the best advantage on the wheel. Some of these trade secrets 

 he unlocked in the first instance from the hearts of their possessors by means 

 of an ounce of tobacco ; he must say that burglars and thieves were much 

 better people than he once believed them to be, and he thought that more good 

 would be done by treating them with kindness than with severity. He had 

 not only to ascertain the power of each particular muscle during life, but 

 to measure its dimensions after death ; but if he measured the cross sections of 

 the muscles of aged people after lingering illness, false results would have 

 been obtained. The cross section of a muscle during life is much larger than 

 after death. So he had to watch for cases of severe accidents in the hospitals, 

 but if a man died a violent death the cause was usually so plain, that the 

 coroner would not order a medical examination of the body, and the friends of 

 the deceased were always in a hurry to " wake" him. Those in Dublin who 

 were executed by the hands of the law were nearly always patriots who had 

 shot their landlords, so they had a vast amount of popular sympathy on their 

 side, and it would have been dangerous for any scientific man to dissect -their 



