CONTLMJOUS YIERATORY MOVEMENT OF ALL MATTER, PONDERiVBLE 

 MD BIPONDEKABLE. 



By L. Maguini. of the Museum of Florence. 



Translated for the Smithsonian Institution.* 



It would bo at onco carious and histructivo, could we uuitc? in one point of view 

 tLe different rellecticnis of mankind on the i)henomena of nature. What variety 

 in ideas ! what ditlerences auioni^ men ! what contrasts between nationalities ! If 

 the ])aths which the human mind pursues could be clearly traced, and it were 

 possible to examine them, we should perhaps discover the reasons which cause 

 men at one time to affirm, as if with intuitive certainty, a principle pregnant with 

 consequences, destined to be confirmed by facts, while at other times they hesitate, 

 go astray, and lose the truth even when earnestly seeking it. 



Our senses, even with the help of the most perfect instriunents, reveal to us but 

 very little al)out nature ; but the sensations derived from the impressiiuis made 

 on our organs by exterior objects are transmitted to the understanding, which 

 co-ordinates them and draws from them the most rational and rigorous deduc- 

 tions ; the small number of facts which our senses thus teach us, afford us the 

 best means of extending our knowledge regarding the external work!. We might 

 repine, witli some justice, at the imperfection of our senses: oar ears might be 

 more impressible, our sense of smell more susceptible; our sight might be even 

 more piercing than it actually is with the aid of optical instruments. Yet it is 

 not difficult to convince ourselves that it is not the senses which deceive us, and 

 that the error proceeds from the deductions formed by the understanding. 



An oar, ])iercing oljliquely a horizontal surface of water, appears to us to be 

 broken at the point where it issues from the water. The ej'e really receives the 

 impres.sions of the light as if the oar were broken. But if our mind were to 

 conclude from this optical phenomenon that we beheld a broken oar, it would 

 not be the eye which was in fault, but the understanding, which deceives itself 

 by a conclusion without verifying the other characters of a broken oar. Tho 

 philosophers who im])ute error to the eye ought, on the contrary, to regard 

 this indication as a signal service ; since, without touching on other properties — 

 the knowledge of which does not pertain to its province — the eye does in fact 

 faithfully r('[)resent to us the real course of the luminous rays which pass from 

 the water into the air. ' 



This example, and a multitude of others of the same kind which might be 

 cited, reach us that it is very dillicult for us to pronounce a correct judgnu-nt in 

 taking our lirst sensations as a basis. It is necessary to wait till new facts add 

 themselves to the old, and disclose the relations which lead to the connnon prin- 

 ciple of all the phenomena of the same order. ^Mathematical truths are niiro 

 conceptions which obey the necessary laws of reasoning; it is not the same case 

 with the physical sciences, the study of which rests not on axioms furnished liy 

 reason, nor on principles which can bo dirccllij drawn from the understanding. 

 Nature ])resent3 us complex j)henonu'na which we must examine minutely, in 

 order to analyze them and discover their cause ; if we would not deviate from 

 reality and truth, we must acce])t the descriptive language of the sensations. 

 The sensations furnish us the data, and the tendency wliicli we have to attributo 

 Ihem to external causes, conducts us from analogy to principles. In reality, iho 



* From Revue des Cours Scicntifi<iues : Purls, No. 41), Nov. 2. 1807. 



