140 THE POPULAR SCIENCE MONTHLY. 



pretation of Nature, if accuracy of vision be thereby impaired. But 

 the term Vorstellungs-fiihigkeit, as used by me, means the power of 

 definite mental presentation, of attaching to words the corresponding 

 objects of thought, and of seeing these in their proper relations, with- 

 out the interior haze and soft penumbral borders, which the theologian 

 loves. To this mode of " interpreting Nature" I shall to the best of 

 my ability now adhere. 



Neither of us, I trust, will be afraid or ashamed to begin at the 

 alphabet of this question. Our first eftbrt must be to understand each 

 other, and this mutual understanding can only be insured by begin- 

 ning low down. Physically speaking, however, we need not go below 

 the sea-level. Let us, then, travel in company to the Caribbean Sea, 

 and halt upon the heated water. What is that sea, and what is the 

 sun which heats it ? Answering for myself, I say that they are both 

 matter. I fill a glass with the sea-water and expose it on the deck of 

 the vessel ; after some time the liquid has all disappeared, and left a 

 solid residue of salts in the glass behind. We have mobility, invisi- 

 bility apparent annihilation. In virtue of 



" The glad and secret aid 



The sun unto the ocean paid," 



the water has taken to itself wings and flown off" as vapor. From the 

 whole surface of the Caribbean Sea such vapor is rising ; and now we 

 must follow it not upon our legs, however, nor in a ship, nor even in 

 a balloon, but by the mind's eye in other words, by that power of 

 Vorstellung which Mr. Martineau knows so well, and which he so 

 justly scorns when it indulges in loose practices. 



Compounding, then, the northward motion of the vapor with the 

 earth's axial rotation, we track our fugitive through the higher atmos- 

 pheric regions, obliquely across the Atlantic Ocean to Western Eu- 

 rope, and on to our familiar Alps. Here another wonderful metamor- 

 phosis occurs. Floating on the cold, calm air, and in presence of the 

 cold firmament, the vapor condenses, not only to particles of water, 

 but to particles of crystalline water. These coalesce to stars of snow, 

 and afterward fall upon the mountains In forms so exquisite that, 

 when first seen, they never fail to excite rapture. As to beauty, in- 

 deed, they put the work of the laj)idary to shame, while as to accuracy 

 they render concrete the abstractions of the geometer. Are these 

 crystals " matter ? " Without presuming to dogmatize, I answer for 

 myself in the aflirmative. 



Still, a formative power has obviously here come into play which 

 did not manifest itself in either the liquid or the vapor. The question 

 now is. Was not the power " potential " in both of them, requiring 

 only the proper conditions of temperature to bring it into action ? 

 Again I answer for myself in the aflirmative. I am, however, quite 

 willing to discuss with Mr. Martineau the alternative hypothesis, that 



