468 Intelligence and Miscellaneous Articles. 



glass for electroscopes, by which these apparatus, especially those 

 with gold and aluminium leaves, often fail in dry air ; for such 

 glass acts like a condenser, and only discharges slowly. It is true 

 that good conducting glass is difficult to meet with. Among 184 

 kinds which I tried 1 only found 19 which I could use, and only 

 three of these were good : the trouble is, however, rewarded by the 

 never failing working of the electroscope. 



If the paper strips are cut off 1 to 2 millim. below the loop, and 

 fine aluminium strips (4 millim. in breadth and 3 to 4 centim. in 

 length, with rounded ends) are fixed on, an electroscope of extra- 

 ordinary delicacy is obtained. My electroscope of this construction, 

 with condensing-plates of 6'5 centim. diameter, gave a deflection of 

 55° when the plates were touched with the poles of a bichromate 

 element, while an ordinary aluminium electroscope showed only 15°. 



With this aluminium electroscope w 7 e can show very distinctly 

 the difference between the arrangement of elements in series and 

 abreast. In the former case, with two Bunsen's elements, the 

 leaves stand almost horizontal. — Zeitschrift fur Pliys. und Client. 

 UnterricJil, vol. iv. p. 182. JBeiblatter der Physik, No. 7, 1888. 



ON THE VELOCITY OF SOUND IN LIQUIDS. BY T. MARTINI. 



The principal results of the investigation are as follows : — 



1. Wertheim's hypothesis that a cylindrical column of liquid 

 vibrates like a solid cylinder is untenable ; the smallness of Wert- 

 heim's numbers arises rather from the influence of the sides of the 

 tubes. 



2. The velocity of sound in water increases w T ith the temperature 

 within the ordinary limits of temperature. 



3. The velocity of sound in other liquids increases with the 

 temperature. 



4. When gases, liquids, or solids are dissolved in water the velo- 

 city of sound increases ; this is also the case with other liquids, such 

 as alcohol, which absorbs water, or turpentine in which resins are 

 dissolved. 



5. The velocity of sound in saline solutions increases with the 

 quantity of salt dissolved. 



6. Solutions of different salts reduced to the same degree of 

 concentration have different velocities. 



7. If the same weight of different salts are dissolved in the same 

 weight of water, very different numbers are obtained ; these are 

 much greater with salts containing water than with anhydrous 

 salts. 



8. If the same weights of anhydrous and of a hydrated salt are 

 dissolved, the velocity of sound in the former is greater than in the 

 latter.— Beiblatter der Physih, No. 8, 1888; horn Atti del. R. 1st. 

 Venet. (6) 6. 



