394 



SCIENCE. 



[Vol. II., No. 33. 



thoiigli somewhat faint, musical sound. About 

 the same result was given hy a disk consisting 

 of the same sheet of tinfoil pasted on card- 

 boai'd. 



Any periodic variation from uniformity in the 

 disk appears to produce corresponding varia- 

 tions ill the magnetic field when the disk is 

 rotated. Depressions made with a punch, at 

 regular intervals, in a zinc disk, rendered it a 

 sound-generator when rotated in this appara- 

 tus. 



Since the jDitch of the note obtained depends 

 only on the number of holes passing the pole of 

 the magnet in a second, it is eas}' to construct 

 a piece of apparatus to illustrate musical inter- 

 vals. A cylinder of galvanized iron, with four 

 rows of holes in the ratio of 4:5:6:8, was 



elearlj- defined, but not so loud as with the 

 other apparatus. Further experiments are in 

 IDrogress. II. S. Cakhaut. 



Evanston, III. 



mounted on a whirling table, and pro^•ided with 

 two U-magnets and two electro-magnets for 

 induction. The latter were placed inside the 

 cjiinder, and the former outside. By means 

 of four kej's, any one of the bobbins, or all of 

 them, can be put in circuit with the telephone. 

 By depressing the keys, the four notes of the 

 common, or major, chord are brought out with 

 great distinctness and clearness. In fact, the 

 intensitj' of the sounds obtained by the mag- 

 netophone is sometimes so great as to be pain- 

 ful to tlie ear when the telephone is held 

 closely against it. 



The above experiment was simplified bj' 

 emplojnng a disk perforated in four concentric 

 circles with 24, 30, 36, and 48 holes respect- 

 ively. A telephone with the mouthpiece and 

 diaphragm removed, was presented to the four 

 rows of holes iu succession, with the production 

 of the four notes of the major chord as before, 



THE WEATHER IN JULY, 1SS3. 



The monthly weather review of the U.S. 

 signal service shows that the most noteworth}^ 

 characteristics of July were the large de- 

 ficiencies iu rainfall in the southern states and 

 in the north-west, the low mean temperature ia 

 nearh' the whole country, and the severe local 

 storms, which were frequently accompanied by 

 lightning and hail. 



The pressure was nearly normal, the de- 

 partures in few instances exceeding .05 inch. 

 The progress of eight depres- 

 sions has been charted. Onl}' 

 one of these passed south of 

 New England, and none visited 

 the southern states. None were 

 traced from the Pacific coast, 

 and four apparentl3' developed 

 in the Rockj'-mountain region. 

 One only of these depressions 

 is deserving of the name of a se- 

 vere storm. This developed in 

 Colorado on the 4th, and reached 

 Nova Scotia on the 7th, accom- 

 panied by heavy rains in the 

 lake region, and violent local 

 winds at Hatteras and Sandy 

 Hook. The storm proceeded 

 across the Atlantic, and on the 

 11th was central off the north- 

 western coast of Ireland, caus- 

 ing heavj- squalls and high seas 

 during its passage. 



The chart of ocean-ice shows, that, since 

 the preceding month, the eastern limit has 

 moved about 2° westward, and the southern 

 limit about 2° northward. There is a marked 

 diminution in the number of icebergs observed, 

 compared with Julj', 1882. 



The temperature has been below the average, 

 except in the Pacific districts, the northern 

 plateau region, the south Atlantic and east 

 gulf states ; but the departures have been 

 small. In New England, the middle Atlantic 

 and west gulf states, the temperature was less 

 than 1° below the normal, while the greatest 

 difference was 3° below in the extreme north- 

 west. A maximum of 112° was recorded at 

 Phoenix, Arizona ; and frosts occurred in north- 

 ern New York, Michigan, Wisconsin, Iowa, 

 New Hampshire, and Pennsylvania. 



The special feature in the precipitation record 



