Notice and description of a Marine Ventilator. 75 



half a century, the existence of southern polar lights, has been fully 

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

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

 age of discoveries, states, that on the night of the 1 6th of Feb. 1 773, 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 the eastward, 

 almost to the zenith and gradually spreading over the whole southern 

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

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

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

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

 cially tliose of a fiery and purple hue." 



As in tlie Aurora desci-ibed 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 we are therefore 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 may be communicated for this Journal. 

 New-Haven, March 2, 1830. 



Art. XV. — JVotice 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 depth, and from three to six feet 

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

 upper and lower, by a horizontal vibrating midriff, suspended upon an 

 axis resting in the middle of the perpendicular sides of the box, and 

 dividing the space into two equal portions. The ends of the box 

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

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

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

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

 perpendicular partition, above and below the axis, and so fitted to the 



