SS6 Mr. Galbraith on the Velocity of Sound. 



the water (on which the effect depends) being diminished by 

 the mixture of the alcohol, is not apparent. 



Another singular example of the agency of heat in effecting 

 a diminution of corpuscular attraction presents itself in the 

 following experiment : — Cut two pieces of soft lead, so that 

 each may have a plain and bright surface ; by pressure these 

 surfaces mav be made to cohere with considerable force. 

 Suspend the' pieces one perpendicularly over the other, and to 

 the lower piece hang weights, nearly as heavy as the cohesive 

 force may be supposed capable of supporting. The applica- 

 tion of a degree of heat, not superior to that of boiling water, 

 will cause a separation, provided the weights be sufficiently 

 heavy : whence the corpuscular force of heat produces sensible 

 effects at minute, even sensible distances. 



The phaenomena of the capillary action of parallel metallic 

 plates are curious. I have made a considerable number of 

 experiments ; but until some difficulties shall be surmounted, 

 they cannot be in a state to be submitted lo public scrutiny. 



An apology is due to you as well as to your readers, for the 

 (Jelay — after I had promised to continue the subject in your 

 last Number : however, I am certain it will not be required, 

 when it is considered that the manufacture of all my own ap- 

 paratus, which the small resources of a country curacy make 

 requisite, often requires ten times the time which the experi- 

 mental researches occupy. In addition, the discovery that the 

 column is suspended by the upper stratum only, rendered the 

 experiments of several weeks quite useless, and demands the 

 application of apparatus of a new construction, which is now 



nearly complete. 



[To be continued.] 



LXV. On the Velocity of Sound. 5j/W.GALBiiAi'rH,£5y.ilf.^. 



To Richard Taylor, Esq. 

 Sir, 



IN the 68th volume of the Philosophical Magazine, page 214., 

 I aave a short paper On the velocity of sound transmitted 

 through the atmosphere. In it I endeavoured to investigate 

 an accurate and commodious formula for determining the ve- 

 locity of sound under given circumstances, embracing all those 

 minutiae affecting it, so far as I was acquainted with them. 

 In a note, (pages 215 and 216,) I mentioned the values of the 

 constant generally introduced in the late investigations of this 

 question, and hinted that a mean of the whole of these, namely 

 r4112j was more conformable to the velocity of sound by ex- 

 periment, 



