1870.] 



Rev. S. Haughton on Animal Mechanics. 



359 



while on the floors of the spots, here and there, were similar single cloud- 

 masses, the distribution of which varied from time to time, the spectrum 

 of these masses resembling that of their fellows on the general surface of 

 the sun. 



I have before stated that the region of a spot comprised by the penum- 

 bra appears to be shallower in the spots I have observed lately (we are 

 now near the maximum period of sun spots); I have further to remark 

 that I have evidence that the chromosphere is also shallower than it was 

 in 1868. 



I am now making special observations on these two points, as I consider 

 that many important conclusions may be drawn from them. 



DESCRIPTION OF PLATE III. 



1. Prominence much bent. 



2. Prominence encroaching over limb — bright line crossing black line. 



3. Black line (F) curved downwards, sometimes nearly touching iron line below- 



O S3 



5. Prominence nearly divided. 



6. Intensely brilliant flashes above and below centres (ofF lines); the interrup- 

 ^ tions very complete. 



^ 7 & 8. Curves in prominence very marked. 



9, 10, 12, 14, 15. My own drawings, made during first and second outbursts. 

 11. A lozenge on the limb as seen with a tangential slit. 

 13. A lozenge as seen on the sun itself. 



VII. " On some Elementary Principles in Animal Mechanics. — 

 No. IV. On the difference between a Hand and a Foot, as shown 

 by their Flexor tendons." By the Rev. Samuel Haughton, 

 F.R.S., M.I). Dubl., D.C.L. Oxon., Fellow of Trinity College, 

 Dublin. Received April 23, 1870. 



The fore feet of vertebrate animals are often used merely as organs of 

 locomotion, like the hind feet ; and in the higher mammals they are more 

 or less " cephalized," or appropriated as hands to the use of the brain. 



The proper use of a hand when thus specialized in its action, is to grasp 

 objects ; while the proper use of a foot is to propel the animal forward by 

 the intervention of the ground. 



In the case of the hand, the flexor muscles of the fore arm act upon the 

 finger tendons, in a direction from the muscles towards the tendons, which 

 latter undergo friction at the wrist and other joints of the hand, the force 

 being applied by the muscles to the tendon above the wrist, and the re- 

 sistance being applied at the extremities of the tendons below the wrist by 

 the object grasped by the hand. 



From the principle of " Least Action in Nature " we are entitled to 

 assume the strength of each portion of a tendon to be proportional to the 

 force it is required to transmit ; and since, in a proper hand, these forces 

 are continually diminished by friction, as we proceed from the muscle to 



