874 
the field for the purpose of making collections, 
and pursuing some investigations upon the re- 
lations of climate and vegetation, and will con- 
tinue both lines of work at the Station; the 
botanical work during the season will be under 
his guidance. Attention will be given to 
general botany, and to the special features of 
the flora of Montana. Mr. R. 8. Williams, of 
the same institution, will spend the month of 
June in making collections in the northwestern 
part of the State, and will be present during a 
part of the session, giving especial attention to 
mosses and ferns. 
No tuition fees are charged either to students 
or investigators; microscopes and glassware are 
supplied free, but the worker is expected to 
meet the cost of material actually consumed. 
Applications and correspondence should be 
addressed to the Director, Professor Morton J. 
Elrod, Missouli, Mont., until July 10th; after 
this date to the Biological Station, Holt, Flat- 
head Co., Mont. 
SYNTONIC WIRELESS TELEGRAPHY. 
AT a meeting of the Society of Arts, on May 
15th, Mr. Marconi read a paper on ‘ Syntonic 
Wireless Telegraphy.’ In the course of his 
paper, according to the report in the London 
Times, he gave an account of two methods by 
which he has been able to arrange a selective 
action in his instruments, so that, for example, 
two stations can converse with each other with- 
out being overheard by an intermediate one. 
In the first he employed an ordinary vertical 
radiator placed near an earthed conductor, the 
effect of the latter being to increase the capacity 
of the radiating vertical wire without increasing 
its radiative power; in this way syntonic re- 
sults were obtained without difficulty. In one 
form of this arrangement the radiating and 
resonating conductors consisted of a cylinder, 
the earthed conductor being placed inside. 
Using cylinders of zinc only seven meters high 
and 1} meters in diameter, good signals were 
obtained between St. Catherine’s Point and 
Poole (50 kilometres distance), which were not 
interfered with or read by other wireless-tele- 
graph installations at work in the immediate 
vicinity. The closely adjacent plates and 
large capacity of the receiver caused it to be a 
SCIENCE. 
(N.S. Vou. XIII. No. 335. 
resonator with a very decided period of its 
own, and, therefore, it was not apt to re- 
spond to frequencies differing from its own 
period, or to be interfered with by stray 
ether waves, such as were sometimes caused 
by atmospheric disturbances, and occasionally 
proved troublesome in the summer. His sec- 
ond syntonized system was the outcome of ex- 
periments with the discharge of Leyden jar 
circuits. Taking for granted that the chief dif- 
ficulty with the old system lay in the fact that 
the oscillations were very dead-beat, he tried, 
by associating with the radiator wire a condens- 
er circuit known to be a persistent oscillator, 
to set up a series of persistent oscillations in 
the transmitting vertical wire. In ene applica- 
tion of this principle the vertical conductor 
was connected to earth through the primary of 
a transformer, the secondary of which was in 
circuit with the coherer, and, ia order to make 
the tuning between these two circuits more 
marked, an adjustable condenser was placed 
across the coherer. To obtain the best results, 
it was necessary that the free period of elec- 
trical oscillations of the vertical wire primary 
of the transformer should be in electrical reso- 
nance with the secondary of the transformer 
which included the condenser. It was easy to 
understand that, if there were several receiving 
stations, each tuned to a different period of 
electrical vibration, of which the corresponding 
inductance and capacity at the transmitting 
station were known, it would not be difficult to 
transmit to any one of them without danger of 
the message being picked up by the others for 
which it was not intended. But, further, it 
was possible to connect to the same vertical 
sending wire, through connections of different 
inductance, several differently tuned trans- 
mitters, and to the receiving vertical wire a 
number of corresponding receivers ; then differ- 
ent messages could be sent by each transmitter 
to the radiating wire simultaneously, and re- 
ceived simultaneously by the vertical wire con- 
nected to differently tuned receivers. A further 
improvement had been obtained by the com- 
bination of the two systems described in the 
paper, the cylinders being connected to the sec- 
ondary of the transmitting transformer and the 
receiver to a properly tuned induction coil, with 
