138 PETROLEUM LAMPS. 
heads of the wild plant are utilized to some extent in the factories. 
The harvest there commences about the middle of July, when the 
flowers have fallen from the heads, and the teasels are of a whitish 
colour. The heads are sorted according to their size, the finest being 
termed "males " and the others " females." The best are those which are 
long, cylindrical, and armed with fine hooks. The produce of each 
head is about five teasels ; but in good soils and favourable seasons it 
reaches seven to nine, which would yield twenty to thirty bales per 
hectare. P. L. S. 
PETROLEUM LAMPS. 
The immense development of petroleum, commonly but erroneously, 
called coal oil, beginning practically in August, 1858, in western 
Pennsylvania, and amounting in the year 1863, in the United States, 
to 6,000 barrels per day, or 2,190,000 barrels per annum, (of which one 
half is exported and the remainder consumed at home,) has directed 
American inventors, within the last three years, to the construction of 
a large number of lamps intended specially fur its consumption. This 
will best be seen by reference to the number of applications presented 
to the American Patent Office during the three years ending 1863, as 
compared with the number for the three preceding years. 
Patents applied for during the three years, ending 1861, 193 ; in 
three years ending 1863, 623. 
This oil is rich in carbon and hydrogen, but void of oxygen ; and 
from the excess of carbon evolved, one main object to be attained was 
to command the oxygen of the atmosphere to affect that degree of com- 
bustion most productive of illumination, and thus at once economise 
oil, obtain a pure white flame, and avoid smoke and unpleasant odour. 
To this end various devices have, within the last three years, been 
patented. 
1. The deflector previously in use has been materially altered in 
form, and in some lamps two or three deflectors within each other, used 
in throwing successive currents of air against the flame above each 
other. 
2. The flat wick has been very generally adopted, being more simple 
and exposing a larger surface of flame to the air. 
3. The glass chimney previously in use, to shield the flame from 
currents of air and to increase the draught and consequent quantity of 
oxygen to the flame, has largely maintained its place. In some models 
the chimney has been extended below the flame, and shortened above 
it ; in others the deflector and chimney have been united ; and in others 
