NAUSCOPIE. 399 



Bottineau's Explanation of Nauscopie, alluded to in Marat's Letter. 



Nauscopie is the art of ascertaining the approach of vessels, or 

 being on a vessel, the approach to land at a very great distance. 

 This knowledge neither results from the undulation of the. waves, 

 nor from quick sight, nor from a particular sensation, but simply 

 from observing the horizon, which bears upon it certain signs indica- 

 tive of the approach of vessels, or land. 



When a vessel approaches land, or another vessel, a meteor ap- 

 pears in the atmosphere, of a particular nature, visible to every eye, 

 without any difficult effort : it is not by the effect of a fortuitous oc- 

 currence, that this meteor makes its appearance, under such circum- 

 stances ; it is,, on the contrary, the necessary result of the approach 

 of one vessel towards another, or towards land. The existence of 

 this meteor, and the knowledge of its different modifications, consti- 

 tute the certainty and the precision of my announcements. 



If I am asked how it is possible that the approach of a vessel to- 

 wards land can cause any meteor to be engendered in the atmo- 

 sphere,, and what affinity exists between two effects so removed ; I 

 reply, that I must be excused giving an account of the why and the 

 wherefore; that it is sufficient I have discovered the fact, without 

 being obliged to explain the principle. 



Do not even the learned acknowledge that the explanation of 

 meteors is often beyond their comprehension ? Valmont de Bomarre 

 says, " Almost all meteors present, in the mechanism of their form- 

 ation, considerable difficulties, profound mysteries, which all the 

 knowledge of philosophers has not yet been able to penetrate." 



After this avowal, it certainly is not my province to explain what 

 the most learned men declare to be inexplicable. 



The meteor of which I am speaking, although manifesting its 

 effects, may conceal its principle; and notwithstanding my discovery, 

 does not the less exist. 



However, the study of twenty years seem to have given me a right 

 to reason upon a subject that has become so familiar to me; and the 

 following is my opinion upon this head. 



The vast expanse of water forms an immense abyss, in which sub- 

 stances of every kind are continually entering. The enormous num- 

 ber of animals, fishes, birds, vegetable and mineral productions, 

 which are decomposed in the vast body of water, produce a continual 

 fermentation of matter, which abounds in spirit of salt, oil, sulphur, 

 bitumen, &c. The presence of these gases is sufficiently apparent, 

 from the smell and disagreeable taste of sea-water. These gases, 

 closely united with the sea-water, remain stationary so long as the 

 waters are quiet and not disturbed ; or they may only experience a 

 slight internal agitation which is manifested externally in a small 

 degree. But when the water is put in motion by stormy weather, or 

 by an active mass which passes over its surface with violence and 

 rapidity (a vessel for instance) then the volatile vapours that are in- 

 closed within the bosom of the deep, escape and rise in smoke (Jumee\ 

 composing a vast envelope around the vessel. As the vessel ad- 

 vances, the envelope advances with it, increasing every instant by 



