SCIENCE AND INDUSTRY. 
During the present century the value of the natural gas used in the 
United States has risen annually from $27,000,000 to $142,000,000. A 
report by John D. Northrop, just published by the United States 
Geological Survey, Department of the Interior, gives statistics of the 
production and consumption of natural gas, and sketches the condition 
of the industry in 25 States. It gives, also, statistics concerning 
gasoline made from natural gas in that year. The recovery of gasoline 
from this source has now become a large industry, which contributes 
materially to the supply of motor fuels. In 1911, there were in opera- 
tion 176 plants, which produced about 7,400,000 gallons of raw gasoline 
from natural gas. .In 1917 — only six years later — there were 886 
plants, which produced nearly. 218,000,000 gallons. 
Prior to 1916 most of the gasoline recovered from natural gas was 
derived from casing-head gas obtained from.oil wells by methods 
involving compression and condensation, but from year to year an 
increasingly large proportion of the annual output of natural-gas 
gasoline has been recovered by the absorption’ process. 
SHEEP-FLY IN GREAT BRITAIN. 
Among sheep-farmers in certain parts of Great Britain the blowfly 
pest is assuming large proportions, states the London Times of 9th 
June. In the past, a check has been kept upon it by reason of the 
fact that there was an adequate supply of farm labour. The Times 
states that— The only method to prevent the fly ‘striking’ is by 
clipping the dirty wool, to keep the flock in a sanitary condition. With, 
perhaps, thousands of sheep on mountain grazings this means an 
immense amount of work, and it is becoming increasingly difficult to 
obtain fell shepherds, because lowlanders are unfitted for the work, 
and the young dalesmen migrate to take up less arduous employment. 
A fly-trapper could set and maintain traps on each sheep farm propor- 
_ tionally to stock and acreage. Although the blue-bottle (Calliphora 
erythrocephala), which invades the butcher’s shop and the housewife’s 
larder, is responsible for some of the stricken sheep, the greater number 
are victims of the green-bottle (Lucilia sericata), the true sheep-fly, 
which causes the poor animal to die an agonizing death. There are, 
therefore, strong compassionate, as well as financial, reasons why 
vigorous steps should be taken to reduce the plague. Thirty or 40 years 
ago, a Coniston gentleman invented an effective trap. It is baited 
with strongly smelling meat or carrion; the flies ascend an upward 
plane, and once inside never discover the aperture by which they 
entered. But shepherds were cheap in those days, and this, combined 
with the prejudices of the dalesmen, led to the neglect of a useful 
invention. Some of these traps are still in existence, and a few years 
ago the manager of the Manchester Corporation’s Thirlmere Estate, 
after considerable trouble, secured oné. Much of Lakeland has been 
converted into a gigantic reservoir, and fly-trapping would be a gain, 
not only to the pastoral industry, but to the public health, for the 
stricken sheep leaves the flock, and almost invariably dies in or near 
a stream.” 
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