830 Tjx'AysACTioM< OF Tffh' Ameiucax Instttutk. 



May 20, 1869. 



Prof. S. D. Tii.LM.v.v, in the chair; Mr. C. E. Emkuv, Serrelary. 

 IvELATIVE YaLUE OF THE SuKEW AND PaDDLE WhEEL, 



Mr. J. K. Fisher fttated be had seen an article in a daily psiper of 

 that day which appeared to him quite remarkable. A paddle-wheel 

 steamer of 400 tons carrying capacity, burning eight tons of coal per 

 day, and making seven and one-half knots per hour, was altered to a 

 screw propeller, carrying 800 tons, and burning but four tons of eoal 

 per day; and yet making better time than when a side-wheel 

 steamer. If this was a fact it was a very important one. 



The Chairman thought there must be some error in the article 

 referred to. A gain of about 100 per cent was not probable, espe- 

 cially as careful experiments have been made with the screw and 

 the paddle wheel, and they were found to be about equal in efficiency. 



Mr. Dudley Blanchard remarked that the paddle wheel has been 

 agreed on as the best for smooth water. A line of screw steamers 

 are now running from here to Boston. They have powerful and 

 well built engines, yet they do not make any better time than pad- 

 dle-wheel steamers. 



S];lf-c;i.()oing Safety Hatch. 

 Mr. George N. Creamer exhibited a model of his safety hatch. 

 The principle on which the hatch works is gravity ; and so perfectly 

 are the ^'eights operating it adjusted that, should a person, or even 

 a weight of a few pounds, be upon the hatch, it will fail to open 

 until the weight is removed, thus, as it will be seen, rendering it 

 impossible for a person to be thrown down the hatchwa}' by having 

 the hatch jerked from under him while standing ui)on it. It can be 

 operated from any floor above or below the hatch which is required 

 to be operated on. When goods are passing through any one hatch 

 all others above and below can be closed. Immediately upon the 

 article of mercliandise having passed, the hatch instantly closes of its 

 own action, thereby receiving the goods, and saving the labor of from 

 three to live men as in many instances. A ]»erson can stand on any 

 floor and operate the hatch either from the top or the bottom. There 

 are two ways of operating the hatch, eitlier by treadle or cord. The 

 hatch has been in use over a year. A Ave story building can be 

 fltted with this hatch for $250, or flfty dollars a floor. 



