326 Intelligence and Miscellaneous Articles, 



parts of which it is composed. By this means, and the rapidity of 

 the motion of the eye, we have always a correct perception of the 

 whole, and gradually we see every part of the picture in its true 

 position. 



The representation on the retina of a whole field of 200° is one 

 of the innumerable and wonderful resources of Nature — in this case 

 being a contrivance by which the beauty of the effect is increased, 

 and by which our attention is gradually called to the various 

 parts which, although not exactly in the direction of the optic axis, 

 and even very far from it, are sufficiently conspicuous and appear to 

 form an interesting or, in any way, a desirable point of observation. 

 By means of this extensive field of vision we are warned of any 

 danger from objects coming to us in the most oblique direction. If 

 a furious animal were running from behind we should see it as soon 

 as it had reached an angle of 1 00° with the optic axis, and this would 

 enable us to take immediate measures for "our safety. But the 

 advantages of an enlarged field of vision are particularly felt in our 

 crowded towns, where we are obliged to be constantly on the look- 

 out for all that is passing around us. 



In every respect the vision of the eyes is as complete and as 

 perfect as can be imagined, and we cannot improve it artificially 

 by single or even double achromatic glasses, which, although mag- 

 nifying considerably the objects, cannot embrace a field larger than 

 the angle formed by the lens at the distance of the eye-glass. 

 With a telescope, if we have the advantage of enlarging a small 

 part of the landscape, we lose the fulness and extent of its pano- 

 ramic beauty. 



Notwithstanding all the resources of the science of optics, no 

 artificial instrument can approach the perfection of the eye ; and it 

 has not yet been given to man even to understand satisfactorily 

 all the laws in accordance with which this marvellous organ has been 

 created, or how it can perform so many wonderful things. 



ON THE CONSERVATION OF ENERGY. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 

 My colleague's letter, published in your Number for August, con- 

 tains a mistake which, if the controversy is continued, I think I 

 ought to rectify. I recollect that Prof. J. Thomson stated to me at 

 Glasgow in 1840, the effects of tidal friction on the earth's rotation ; 

 but it was at the subsequent Meeting of the British Association in 

 Glasgow that I had the honour of being President of Section A. 

 This fact divests the communication of the semipublic character 

 attributed to it by Prof. Tait. 



I am, Gentlemen, 



Your obedient Servant, 

 University of Edinburgh, Philip Kelland. 



September 12, 1863. 



