Notice and dtscnptloyi of a Marine Ventilator. 15 



half a century, die existence of soutliern polar lights, has been fully 

 established. Besides earlier notices in the Philos. Trans. Mr. Fors- 

 ter who, as a naturalist, accompanied Captain Cook in his second voy- 

 age of discoveries, states, that on the nigluof the 16th of Feb. 1773, in 

 S. lat. 58^, a beautiful phenomenon was observed and was exhibited 

 during several successive nights- " It consisted of long columns of 

 a clear white light, shooting up from the horizon to tlic eastward, 

 almost to tlie zenith and gradually spreading over the whole soutliern 

 part of the sky. These columns were sometimes bent sideways at 

 their upper extremities ; and though in some respects similar to the 

 noithcru lights of our hemisphere, yet differed from them in being 

 always of a whitish color ; whereas ours assume various tints, espe- 

 cially those of a fiery and purple hue." 



As in the Aurora described by Mr, Bowdoin, and seen also by his 

 observing friends, the columns were perfectly irised and very strong- 

 ly resembled the regular segments of a fine rainbow, both in form and 

 in the disposition and arrangement of colors, it would seem that the 

 appearance if it should not, on fuller examination, prove to be novel, 

 is probably uncommon ; and w^e are tlierefore much obliged by his 

 communication. If similar facts gathered either from reading or ob- 

 servation are within the knowledge of any person it is respectfully re- 

 quested that an account of them maybe communicated for this Journal. 



New-Haven, March 2, 1830. 



Akt. XV. — Notice and description of a Marine Ventilator ; by 



Samuel Whiting. 



The marine ventilator consists of a box, or chest, of dimensions 

 to adapt it to the vessel in which it is used, say from six to twelve 

 feet long; from two to four feet in deptli, and from three to six feet 

 wide. This box, or chest, is divided into four compartments, to wit, 



and 



axis 



dividing the space into two equal portions- The ends of tl)e box 

 form segments of tlie circle which would be described by a revolu- 

 tion of the midriff upon its axis, so that in the vibrations of the mid- 



1 



:ifF, as little air as possible may escape from one compartment to the 

 other. These upper and lower spaces, are subdivided by xi middle 

 pernendicular nartition, above and below the axis, and so fitted to the 



V 



