506 PHILOSOPHICAL TRANSACTIONS. [anNO 1795. 



were suddenly drawn under water, and remained so for a short space of time, 

 which indicates, that either there must have been at that time a swell in the sea, 

 or a depression or sinking of the earth under it. 



From what we have seen lately here, and from what we read of former erup- 

 tions of Vesuvius, and of other active volcanos, their neighbourhood must al- 

 ways be attended with danger ; with this consideration, the very numerous popu- 

 lation at the foot of Vesuvius is remarkable. From Naples to Castel-a-mare, 

 about 1 5 miles, is so thickly spread with houses as to be nearly one continued 

 street, and on the Somma side of the volcano, the towns and villages are scarcely 

 a mile from each other ; so that for 30 miles, which is the extent of the basis of 

 Mounts Vesuvius and Somma, the population may be perhaps more numerous 

 than that of any spot of a like extent in Europe, in spite of the variety of dan- 

 gers attending such a situation. 



V. Neiu Observations in further Proof of the Mountainous Inequalities, Rota- 

 tion, /Atmosphere, and Twilight, of the Planet Venus. By John Jerome Schro- 

 eter, Esq. Translated from the German, p. 117- 



Though it is a satisfaction to me, says Mr. S., that Dr. Herschel last year 

 found my discovery of the morning and evening twilight of Venus's atmosphere to 

 be confirmed, as I could not hope to have obtained such an important con- 

 firmation so early, considering the excellent telescopes required, and that a favour- 

 able opportunity for such observations occurs but seldom ; yet the paper on the 

 planet Venus, which this great observer has inserted in the Philos. Trans, for 1793, 

 contains unreserved assertions, which may be easily injurious to the truth, for the 

 very reason that they have truth for their object, and yet rest on no sufficient 

 foundation. Openness, without reserve or indirect views, must guide the spirit 

 of observation in the true inquirer into nature, and be his sole object. To this 

 pure source alone can I ascribe what is said in the above-mentioned paper, so as to 

 reconcile it to the friendly sentiments which the author has always hitherto ex- 

 pressed toward me, and which I hold extremely precious ; though perhaps to 

 others it may not have the same appearance. But this very object makes it also 

 my duty to be equally unreserved in remarking what truth is, and demands ; 

 particularly as evident misunderstanding and error appear to have chiefly occa- 

 sioned those assertions ; which most probably would not have been thus made, 

 if the author had then known of my very circumstantial memoir, which was 

 read at the jubilee of the university of Erfurt, in a meeting of the Electoral 

 Academy of Sciences, and which they ordered to be printed ; and could have 

 compared the many careful observations, full of matter, contained in it. There- 

 fore, in order to prevent misapprehensions, let me be allowed to make some re- 

 marks, which truth requires of me, before I communicate faithfully, as I mean 



