SCIENTIFIC SUMMARY. 
443 
The Harmonic Engine . — One of the most remarkable of Mr. Edison’s many 
inventions is the so-called harmonic engine, which consists primarily of a 
large tuning-fork put into vibration by means of an electric current. With 
a small battery and a couple of electro-magnets, Mr. Edison has succeeded in 
getting sufficient power out of the vibrations of this “ tuning-fork ” to pump 
up a considerable quantity of water to the top of his house, to drive a 
sewing-machine, or to perform other work requiring small power. The 
“fork” consists of a couple of limbs, 2\ feet long, made of 2-inch square 
steel, the curved part being firmly held in a casting bolted to a solid founda- 
tion. Attached to the end of each arm is a 351b. weight, and near each is 
a small electro-magnet, possessing sufficient power to set the arms in vibra- 
tion. These vibrations, which are made at the rate of 35 per second, are of 
small amplitude, but are of sufficient power to work a little pump, the 
rapidity of the motion compensating for the smallness of the stroke. The 
machine is at present little more than a toy, but, its effectiveness having- 
been demonstrated, further developments may render it a useful motor for 
employment in domestic work. Mr. Edison proposes to utilize the machine 
for compressing air, but it will probably be found more profitable to employ 
the power direct, instead of using it through that agency, the machinery for 
which must of necessity absorb a considerable quantity of the power in over- 
coming friction. 
ZOOLOGY. 
The Buzzing of Insects . — It has long been supposed that the buzzing of 
bees, flies, and other insects, was due to the friction of the air passing 
through the thoracic stigmata, after being set in motion by the action of the 
muscles moving the wings. After repeating the experiments on which this 
opinion is founded, M. Perez comes to a different conclusion. He finds that 
when the wings of a fly are held so tightly that no motion of their bases is 
possible, no sound is produced ; but, on the other hand, the removal of the 
scaly portions fringing the periphery of the stigmata, injury to the margins 
of the stigmata themselves, and stopping them with solid masses, leaves the 
buzzing unaltered, and even a hermetical closure of these apertures has only 
the effect of weakening the sound produced. In this last case the power of 
flight is weakened, owing, according to M. Perez, to an asphyxia of the 
insect caused by the exhaustion of the air in the thoracic tracheae, which is 
after a time made up by an influx of air from the abdomen, but the attempts 
at flight become weaker and weaker, and the animal speedily dies. 
M. Perez’s interpretation of these phenomena is that the causes of buzzing 
reside solely in the wings. Cutting the wings influences the buzzing more 
or less, this becoming thinner and sharper and losing the softness due to the 
friction of the air upon the edges of the wings. The sound is different 
according to the amount of the wing removed, that is to say, the shortness 
of the stump, and it is in relation with the beatings of the stump against 
the solid parts which surround it, or of the horny pieces which it contains 
one against the other. If the section be carried down to sensitive parts the 
sound ceases ; but this is because the animal ceases to perform movements 
which have become painful to it. 
