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THE POPULAR SCIENCE MONTHLY. 



mit that parasites in many cases do no per- 

 ceptible harm. To these cases may be op- 

 posed the numerous instances in which they 

 have proved destructive to their hosts, 

 whether animals, birds, or men, often car- 

 rying off multitudes of creatures when they 

 become excessively abundant on a species ; 

 and in the most favorable cases they give 

 the host discomfort and inconvenience, 

 though their work mavbe overlooked in the 

 presence of his superior vigor. As a rule, 

 parasites belong to the lower orders of 

 animals worms or insects. Sometimes an 

 arachnoid or a crustacean will join the com- 

 pany ; but a few small fishes are the only 

 creatures among the vertebrates that ever 

 assume that relation. The stories that have 

 been told of the existence of other inhabit- 

 ants in the system are either fables or have 

 originated in the accidental presence of sin- 

 gle individuals who were probably as much 

 astonished as their host at finding them- 

 selves in such a home. 



The Repeating Melograph. M. J. Car- 

 pentier exhibited, at the recent electrical 1 

 exhibition in Paris, an instrument called the 

 repeating melograph, by means of which, he 

 claimed, any piece or improvisation which 

 a composer may play on the key-board to 

 which it is attached is registered, and may ! 

 be repeated upon any other instrument \ 

 with which it may be connected. It, more- 

 over, secures the repetition, not of the 

 piece only, but of the style, even to the j 

 false notes, of the player. Both processes, 

 the registering and the repeating of the 

 piece, are performed through the medium 

 of electric currents. In the former case the 

 keys of the instrument on which the piece 

 is played are connected with wires through 

 which a current is established when the key 

 is pressed down. This current sets in oper- 

 ation an apparatus, with tools answering to 

 the several keys, by means of which a per- 

 foration corresponding in character with 

 the musical value of the note is made in a 

 moving band of paper. The piece being 

 finished, the band is ready to serve in a 

 second execution of it. Electric communi- 

 cation is effected between the perforated 

 band and the second instrument ; and a 

 current is formed, causing a corresponding | 

 key to be sounded at each perforation of j 



the band as it passes the circuit in the pro- 

 cess of unrolling. M. Carpentier contem- 

 plates adjusting his instrument so that it 

 may also be made to print the piece in or- 

 dinary musical type. 



Electric Units. The International Con- 

 gress of Electricians at Paris unanimously 

 agreed upon a uniform standard of electric- 

 al units of measurements. It decided to 

 adopt the fundamental units, the centime- 

 tre, the gramme, the second (C. G. S.); 

 that the practical units, the ohm and the 

 volt, should be defined, as now, the ohm as 

 10 9 , and the volt as 10 8 ; that the unit of 

 resistance (ohm) be represented by a col- 

 umn of mercury having a section of a square 

 millimetre at the freezing-point, and a 

 height to be determined experimentally by 

 the International Committee ; that the cur- 

 rent produced by a volt in an ohm be called 

 an ampere instead of a w-eber, the latter 

 name having been applied by Weber him- 

 self in Germany to a current of ten times 

 less force ; that the name of coulomb be 

 applied to the quantity of electricity defined 

 by the condition that an ampere gives a 

 coulomb a second, the former English we- 

 ber ; and that the name farad be applied to 

 the capacity defined by the condition that a 

 coulomb in a farad gives a volt which is 

 equivalent to the farad of the British Asso. 

 ciation. The Carcel lamp was recommended 

 to be continued as the standard for the com- 

 parison of lights, pending the investigations 

 of an International Committee to ascertain 

 and fix upon the most practicable standard. 



"Clonds of Seeds." A correspondent 

 of " La Nature " describes a remarkable ap- 

 pearance of seeds in the air that was ob- 

 served in Guatemala during eight consecu- 

 tive days in February last. In the early 

 hours of the afternoon it was easy to per- 

 ceive at a certain distance from the ground 

 bodies resembling snow-flakes, which ap- 

 peared and disappeared instantaneously, 

 generally going in the same direction, but 

 which were visible only when they passed 

 between the sun and the observer. They 

 moved gracefully, with variegated colors, 

 falling and then rising out of sight, as snow- 

 flakes do when they melt in the air; at 

 other times they were carried along by the 



