524 KOVtTM ORGANtJM [rOOK 11. 



sensible by tlie accumulation of motion ; that wbicli is imper- 

 ceptible from its velocity, has not as yet been well measured ; it 

 is necessary, however, that this should be done in some cases, 

 with a view to a proper investigation of nature. 



The sixth case, where the sense is impeded by the power of 

 the object, admits of a reduction to the sensible sphere, either 

 by removing the object to a greater distance, or by deadening 

 its effects by the interposition of a medium, which may weaken 

 and not destroy the object ; or by the admission of its reflection 

 where the direct impression is too strong, as that of the sun in 

 a basin of water. 



The seventh case, where the senses are so overcharged with 

 the object as to leave no further room, scarcely occurs except in 

 the smell or taste, and is not of much consequence as regards 

 our present subject. Let what we have said, therefore, suffice 

 with regard to the reduction to the sensible sphere of objects not 

 naturally within its compass. 



Sometimes, however, this reduction is not extended to the 

 senses of man, but to those of some other animal, whose senses, 

 in some points, exceed those of man ; as (with regard to some 

 scents) to that of the dog, and with regard to light existing 

 imperceptibly in the air, when not illuminated from any ex- 

 traneous source, to the sense of the cat, the owl, and other 

 animals which see by night. For Telesius has well observed, 

 that there appears to be an original portion of light even in the 

 air itself,'' although but slight and meagre, and of no use for the 

 most part to the eyes of men, and those of the generality of 

 animals ; because those animals to whose senses this light is 

 proportioned can see by night, which does not, in all probability, 

 proceed from their seeing either without light or by any internal 

 light. 



Here, too, we would observe, that we at present discuss only 

 the wants of the senses, and their remedies ; for their deceptions 

 must be referred to the inquiries appropriated to the senses, and 

 sensible objects ; except that important deception, which makes 

 them define objects in their relation to man, and not in their 

 relation to the universe, and which is only corrected by universal 

 reasoning and philosophy.'' 



■ Riccati, and all modern physicists, discover some portion of light 

 in every body, which seems to confirm the passage in Genesis that 

 assigns to this substance priority in creation. Ed. 



^ As instances of this kind, which the progress of science since the 

 time of Bacon aflford, we may cite the air-pump and the barometer, for 

 manifesting the weight and elasticity of air : the measurement of tha 

 velocity of light, by means of the occultation of Jupiter's satellites 

 and the aberration of the fixed stars : the experiments in electricity 

 mad galvanism, and in the greater part ot pneumatic chemistry. In 



