TOL. XLVII.] PHILOSOPHICAL TRANSACTIONS. . 1Q5 



it struck the back of his hand; nor did he hear the crack, though the bystanders 

 said, it was a loud one; nor did he particularly feel the stroke on his hand, 

 though he afterwards found it had raised a swelling there of the size of half a 

 swan-shot or pistol-bullet. His arms and the back of his neck felt somewhat 

 numbed the remainder of the evening, and his breast was sore for a week after, 

 as if it had been bruised. From this experiment may be seen the danger, even 

 under the greatest caution, to the operator, when making these experiments 

 with large jars; for it is not to be doubted, but that several of these fully 

 cliarged would as certainly, by increasing them, in proportion to the size, kill a 

 man, as they before did the turkey. 



On the whole, Mr. Franklin appears in this work in the light of a very able 

 and ingenious man; that he had a head to conceive, and a hand to carry into 

 execution, whatever he thought might conduce to enlighten the subject of which 

 he was treating; and though there are in this work some few opinions, in which 

 Mr. W. could not perfectly agree with him, he thought scarcely any body was 

 better acquainted with the subject of electricity than Mr. F. was. 



XXXII, On Dr. Hales's Ventilators; also the Temperature and Saltness of the 

 Sea, &c. By Captain Henry Ellis* F.R.S. dated Jan. 7, 1750-51, at 

 Cape Monte Africa, Ship Earl of Halifax, p. 211. 



The following is a detail of the experiments, which Capt. E. made to prove 

 the utility of the ventilators. 1 . He took a wax candle, of 8 to the pound, and 

 drew it through a mold, to make it of one thickness from end to end: then 

 weighed it exactly, and lighted it in the ship's hold: where it wasted 67 grains in 

 30 minutes; that place not being ventilated during 24 hours, but after 6 hours 

 ventilation it wasted 94^- grains in the same time. 



2. He carried into the hold a plate of silver, well polished, and a lantern and 

 candle, all blinded, except a round hole of about 2 inches diameter. He placed 

 the plate at 6 feet distance from it; and with such obliquity, that the rays from 

 the light should fall on its surface at an angle of 45 degrees. He then fixed a 

 white paper screen, at the same distance from the plate, and at the same angle as 

 the lantern, so that the reflected rays might fall on it also. This done, he ob- 

 served, that the reflection from the plate distinctly was only 17"" 30* with an 

 unventilated hold; it being turned the colour of tarnished lead; where<is, when 

 the air was replaced by 4 hours ventilation, it continued to reflect light, and 

 retain its brightness 4*^ 47". 



3. The ship's bell, whose diameter is 14 inches, he had brought into the hold, 

 when ventilation had been omitted 1 2 hours. Having hung it under the lower 



• Who published an account of his voyage to Hudson's Bay, 

 CC 2 



