388 Mr. T. Proctor Hall on New Methods of 



similar way the tension of metallic wires at or near their 

 melting-points. 



From measurements of pendent drops of water Worthington* 

 found T=75 dynes at 16° C. (77 at zero). 



Henry | and YoilleJ measured the contractile force of soap- 

 bubbles formed on U-tubes. 



Dupre § suggested that the existence of a distinct tension 

 in a soap-film might be shown by its effect upon a straight 

 wire laid across the legs of another U-shaped wire when a 

 film is formed between. 



Yan der Mensbrugghe || had already measured the tension 

 of such a film in a wire frame by finding the weight supported 

 by the free end of a string which was fastened to the frame 

 and looped within it, so that the film was bounded by the 

 greater part of the wire frame together with the outer edge of 

 the circular loop. 



Yan der Mensbrugghe H also added weights to the lower of 

 two equal horizontal circular wire rings until the barrel- 

 shaped bubble formed between them became cylindrical. 

 Sondhauss**, who employed the same method, dispensed with 

 the lower ring and suspended the upper from the arm of a 

 balance above the liquid. In this way he obtained as an 

 approximation T=76 — *186 £ dynes for water between 1°'6 

 and 16°-6 C. Timbergft foumlT = 80-8--22:U dynes, using 

 for calculation the maximum increase of weight as the ring is 

 raised from the water-surface. Cantor ft calculated the ratio 

 of the maximum weight to the surface-tension, and found for 

 water T=72'3 dynes at a temperature not stated. 



Terquem§§ connected the ends of a horizontal wire by two 

 equal strings to the ends of another wire of the same length 

 above it. He then hung a small weight to the lower wire 

 and measured the curvature of the strings when a film was 

 formed between them. 



Magie || || measured the curvature of the lower part of the 

 meniscus in a capillary tube, and concluded that if any contact- 

 angle exists at all when the liquid wets the tube it is very 

 small. He found for water at 19°'25C., T = 70"9 dynes (73'6at 



* Proc. Roy. Soc. xxxii. p. 362 (1881) ; Phil. Mag. Jan. 1885, p. 46. 



t Phil. Mag. June 1845, p. 363. 



% Jour -n. de Physique, iv. p. 333. 



§ Theorie meeanique de la Chaleur, 1869. 



|| Phil. Mag. April 1867, p. 270. 1) Ibid. 



** Pogg. Ann. Erg. viii. (1878) p. 266. 



tt Wied. Ann. xxx. p. 545 (1887). f % Ibid, xlvii. p. 399 (1892). 



§§ Journ. de Physique, vii. p. 406 (1878). 



IIH Wied. Ann. xxx. p. 432 (1885). 



