784 
NATURE 
[JuNE 9, 1923 

future. Radio telegraphy as conducted at present 
causes great disturbance. The power stations produce 
great explosions in the ether, the waves sent out 
having a wide range of frequencies which interfere 
with all forms of radio receiver. At present the radio 
engineer has utilised all the audio range of frequencies 
and ‘several octaves of the radio frequency range. 
General Squier’s plan is to utilise the infra audio 
range of frequencies, which are not used at present. 
An advantage of his system is that it cannot interfere 
with radio receiving. When applied to submarine 
telegraphy a modulating frequency of to per second 
corresponds to 75 words per minute, which is far 
higher than any form of sound reception. 
AT a meeting of the Optical Society held on 
Thursday, May 24, Mr. R. S. Whipple, vice-president, 
in the chair, the sixth of the series of lectures on the 
evolution and development of optical instruments 
was delivered by Mr. David Baxandall, the subject 
being ‘‘ Telescopes before the early part of the roth 
century.’’ The period from the time of Roger Bacon 
(d. 1292) to the beginning of the 17th century was 
dealt with at some length, particular attention being 
directed to William Bourne’s description (1585) of a 
12-inch perspective glass of about 15 feet focal 
length, which gave telescopic vision and magnified 
distant objects about twenty times. The invention 
of the telescope with concave eyelens by Hans 
Lippershey in 1608 was then dealt with and William 
Gascoigne’s description of the way he arrived at the 
invention of telescopic sights quoted. The invention 
of the Gregorian and Newtonian reflecting telescopes 
was next referred to, and followed by a description of 
Hadley’s reflector. The work of Chester Moor Hall, 
and the researches and work of John Dollond and 
Peter Dollond on the development of the achromatic 
lens, were also discussed. The lecture was illustrated 
by a number of pictures of old telescopes and by 
exhibits from the Science Museum, which included 
an early Italian telescope, and object-glasses or 
telescopes by various telescope-makers from the latter 
part of the 17th until the early part of the 19th 
century; the original glass negative made by Sir 
John Herschel in 1839; William Herschel’s polishing 
machine, and the 7-foot reflector with which he 
discovered the planet Uranus. A number of these 
examples are from Mr. Thomas H. Court’s collection 
in the Science Museum. 
Capt. R. AMUNDSEN hopes to undertake his 
projected flight across the North Pole about the 
end of June. After a visit to Nome, Capt. Amundsen 
returned to Wainwright, his winter quarters near 
Cape Barrow, the most northerly point of Alaska, 
in April last. The Norwegian Storthing has voted 
60,000 kroner for an expedition to go to his support 
on the European side of the polar basin. In an 
article in the Times Mr. H. W. Sverdrup, second in 
command of the Maud, discusses the prospects ofa 
successful flight to Spitsbergen or Cape Columbia 
in Grant Land. Capt. Amundsen has been provided 
by the United States Coast and Geodetic Survey 
with a Fischer sextant with an artificial horizon. 
NO. 2797, VOL. 111] 

This should allow him to measure the altitude of 
the sun with an exactness of 10’ to 20’ and possibly 
1’ to 2’. If, however, the sun is obscured, Capt. 
Amundsen will require to fly by compass only. In 
this case he will have to change his course every now 
and then in order to follow a meridian from Point 
Barrow to the Pole, whereas from the Pole a constant 
course can be kept. If solar observations are im- 
possible, there is only the actual flying time on which 
to calculate the position. Sixteen hours from Point ~ 
Barrow should take the airman to the Pole, from 
which a compass course of N. 171° W. should land 
him on Spitsbergen. The difficulty will be to estimate 
leeway, etc. A contrary wind of about Io metres a 
second would allow the aeroplane to reach only 
lat. 85° N. after sixteen hours’ flight, and a course 
of N. 171° W. from there would take it to the New 
Siberia Islands. Mr. Sverdrup agrees that the 
prospects for a successful flight to Cape Columbia 
must be considered more favourable. 
Ar the annual meeting of the Illuminating Engineer- 
ing Society on May 24, the report of the Council 
contained a summary of much varied and useful 
work. A joint committee, on which the Society 
and educational bodies will be represented, is to be 
appointed to consider courses of instruction in 
illuminating engineering, and the preparation of a 
suitable textbook for the use of students. Dr. 
J. F. Crowley presented a paper on “‘ The Use of 
Synchronously Intermittent Light in Industry,” 
which was illustrated by some striking experiments. 
The development of the neon lamp, which can be 
completely extinguished and lighted at a high 
frequency, has revolutionised methods and led to 
important industrial developments. By the aid of 
an oscilloscope utilising such lamps fed by an alternat- 
ing current of regulated frequency, the motions of a 
high-speed machine can be apparently slowed down 
until they are almost stationary. Thus the move- 
ments of the mechanism of a sewing machine, 
illuminated by the intermittent light of a neon lamp, 
can be followed with perfect ease and any small 
irregularities observed at leisure. The method has 
been applied to many problems involved in textile 
machinery, where exact and regular speed-regulation 
is of great importance ; and in other cases it is possible 
to detect and observe such phenomena as undue 
play at bearings, effects with whirling shafts, etc., 
which are quite unrecognisable by ordinary steady 
light. Mr. P. R. Ord also demonstrated the use of 
the Nutting-Hilger spectrophotometer for the com- 
parison of natural and artificial daylight, an apparatus 
which affords valuable information on the colour- 
revealing qualities of such lighting units. A number 
of curves were shown to illustrate the departure from 
normal daylight and the extent of the variations in 
the spectrum of daylight at different times in the © 
day. 
Many optical instruments, in the construction of 
which prisms form an essential part, are grouped — 
together in a new catalogue which has just been a n 
issued by Mr. John Browning, of 37 Southampton 

