Vol. liii.] philosophical transactions. 6q5 



to light candles to see to dine, at one o'clock, though the table was placed close 

 by two large windows. About 3 the darkness became more horrible, which aug- 

 mented till half past 3, when the wind breezed up from the s.w., and brought 

 on some drops of rain, or rather sulphur and dirt, for it appeared more like the 

 latter than the former, both in smell and quality. Mr. S. took a leaf of clean 

 paper, and held it out in the rain, which rendered it black whenever the drops 

 fell upon it; but when held near the fire turned to a yellow colour; and 

 when burned it fizzed on the paper like wet powder. During this shower the 

 air was almost suffocating with a strong sulphureous smell ; it cleared up a little 

 after the rain. There were various conjectures about the cause of this natural 

 incident. Some imagined it might have been occasioned by the burning of the 

 woods ; but Mr. S. thinks it most probable, that it might have been occasioned 

 by the eruption of some volcano or subterraneous fire, whence the sulphureous mat- 

 ter may have been emitted in the air, and contained in it until meeting with some 

 watery clouds, it has fallen down together with the rain. 



XFI. Of a Remarkable Marine Insect.* By Mr.jlndrew Peter Du Pont. p. 57. 



In a calm on his voyage to England, on board the Friendship, Capt. Thompson, 

 two persons swimming took up this most singular creature floating on the sur- 

 face. Its motions muscular. Its length a little more than 1 inch. Four small 

 and short horns, probably its eyes. It protruded them in the water only ; an 

 orifice in the front part, seemingly its mouth. Two round spots opaque, possibly 

 respiracula. The mid-line of the back part appeared through a common magnifier 

 like a silver leaf, and was in continual undulating motion, either from the muscles 

 or circulation of juices. Two side lines extending the whole creature's length, 

 and ending in one in the tail of a deep blue. The claws, or tentacula, end in 

 a deep blue ; a silvery cast intermixed with the blue over the whole back, or up- 

 per parts, where the blue is lighter. It can turn itself on the back by a muscu- 

 lar contraction of the head part, the tail, and ramified arms inwards. The in- 

 ferior parts are white. It died the third day, though the water was shifted once 

 every day. 



XFII. On the late Transit of Venus. By M. IVargentin, Sec. to the Royal 

 Acad, of Sciences in Sweden, p. 59. 



The observations on the last transit of Venus over the sun, made at the Cape 

 of Good Hope, are excellent, and seem to decide, that the horizontal parallax of 

 the sun is S'^l or 8'''. 3 at most. Mr. W. had before found it to be that quantity, 



* The aniraal here described and figured by Mr. Du Pont is not an insect, but belongs to the 

 Linnaean tribe of Mollusca, and is the Doris radiata of the Gmelinian edition of the Systeraa 

 Naturae. 



