roL. XXV. No. 5.] 
POPULAR SCIEI^rCE l^EWS. 
71 
Sf^e J^opcalai" (§eienGe I^ew§. 
BOSTO>r, MAY 1, 1891. 
JUSTIN P. NICHOLS, S. B Editor 
ILLIAM J. EOLFE, LiTT. D. . . ASSOCIATE Editor 
The price of illuminating gas supplied by vari- 
lus private companies in England during the year 
90 varied from 43 cents to §1.87 per thousand 
t, while the price of gas supplied by city and 
wn governments varied from 45 cents to .§1.50. 
't is worthy of particular notice that the returns 
show that in the works of private companies 267 
cubic feet more gas are obtiiined, on an average, 
from a ton of coal than in those under the man- 
agement of local authorities. These figures do 
not give much encouragement to the rather nu- 
merous class of persons who think that all indus- 
* trial enterprises should be under governmental 
control, and particularly that the manufacture- of 
gas and electricity should be undertiikeu by muni- 
cipal or town authorities, — especially when it is 
remembered that, on the whole, the political 
affairs of Knglish cities and large towns are more 
eflBcieutly and economically managed than with us. 
At a scientific meeting recently held in Lyons, 
it was stated that an alkaloid either identical with 
or closely allied to quinine had been produced in 
Germany, and that in doses of 25 to 50 cgtns. it 
had been successful in eradicating intermittents 
of long standing, but that it did not seem to pos- 
sess the same success in reducing the temperature 
in cases of pneumonia or of phthisis. The empir- 
ical formula of natural quinine is C^, Hj, X^ Oj, 
and every one familiar with organic chemistry 
can see how many possible isomeric bodies this 
formula is capable of producing. The chemical 
constitution of the .artificial alkaloid is expressed 
by the term metamidophenjlparamethoxychino- 
lin ; and, although it is probably an isomer of the 
true quinine, it may prove an efficient substitute 
in many cases, provided the cost of manufacture 
is not greater than that of the natural alkaloid. 
PrROGRAVXTRE is a new art process recently 
perfected by a French inventor, iind is a modifica- 
tion of the old-fashioned "hot-poker" drawings. 
The graving tool consists of a hollow pointed 
platinum tube raised to incandescence by the 
combustion of a mixture of gas and air in its inte- 
rior. With this white-hot point any desired de- 
sign may be drawn or copied upon wood, faljrics, 
leather, etc., giving a most beautiful effect of 
shading in rich browns or black, due to the more 
or less perfect carbonization of the material. The 
manipulation of the tool is easy, and anyone with 
sufficient talent to draw at all can easily learn 
to manage it and produce beautiful and artistic 
•work. 
Investigations carried on in England during 
the past winter upon the effect of fog upon plants, 
jhave shown that iu the country the fog has no 
iirect injurious effect upon vegetation, but in 
andon and other large cities the reverse is the 
se. A.t Kew and at Chelsea scrapings were 
aken from twenty square yards of the roofs of 
glass houses which had been well washed down 
before the commencement of the spell of fog. In 
oth cases the weight of deposit was about the 
lame — thirty-one grains, per square yard, or six 
ons per square mile. An analysis of the deposit 
rom Chelsea shows about 40 per cent, of mineral 
natter, 36 per cent, of carbon, and 15 per cent, of 
hydrocarbons, whicli last item explains the ole- 
aginous character of London fogs. The sulphuric 
acid was found to be nearly 5 per cent., and the 
hydrochloric acid I14 per cent. From 2 to 3 per 
cent, of metallic iron in minute particles was also 
found — a fact of some importance, for iron salts 
deposited on foliage are known to be injurious. 
The above analysis well explains the oft'ensive 
nature of the celebrated London fogs, ))oth to 
plants and animals; and the only method sug- 
gested to obviate the injury to plants in green- 
houses is the rather impracticable one of covering 
the house with canvass during the prevalence of 
fogs, or making it as nearly air-tiglit — or rather 
fog-tight — as possil)le. Fortunately there are few 
or no localities in this country which can be com- 
pared with the British metropolis, either in regard 
to the quantity or quality of precipitated atmos- 
pheric moisture and impurities. 
An interesting application of the well-known 
principle of the variable electrical conductivity of 
the element selenium under the influence of light 
rays, has been made by Professor Barton, of the 
Lick Observatory, in the construction of an auto- 
matic comet-seeker. A prism is placed in front 
of the object-glass, but instead of the ocular there 
is a met.allic diaphragm with slits in the position 
of the three hydrocarbon bands in the yellow, 
green, and blue. Light passing through these 
slits falls on a plate of selenium which forms one 
side of a Wheatstoue bridge, connected to a bat- 
tery and an alarm. ITie telescope is made by au- 
tomatic machinery to sweep the semi-diurn.al arc 
in about ten minutes, and then, after shifting 
northwards about two-thirds of the " field," 
sweeping back again. ITie light of the continu- 
ous spectrum of Sirius is insufficient to disturb 
the "bridge"; but with the faintest comet, the 
prism analyses the light into brigiit lines winch 
disturb the balance of the Wheatstone bridge, and 
a current is sent to tlie alarm bell. Further par- 
ticulars of what promises to be a very valuable 
invention will be awaited with interest. 
The New York legislature has been devoting 
its attention once more to the much-abused oleo- 
margarine, and has succeeded in passing a law 
absolutely prohibiting its use by keepers of ho- 
tels, boarding-houses, restaurants, etc., not only 
for their guests, but for their employes as well. 
It is but a step from this to a law forliidding any 
person to knowingly make use of artificial butter 
iu his own home ; and th(! day may not be far oft 
when the daily diet of the h.appy citizens of the 
Empire State may be regulated by an obligatory 
bill of fare, prepared every twenty-four hours by 
a political "Commission" at Albany, and tele- 
graphed on the previous evening to the various 
cities and towns, in the same way as the daily 
weather predictions are now distributed. 
WHAT WE OWE TO GAS WORKS. 
The first instance of practical gas lighting on 
record occurred in the year 1792, when one 
William Murdock lighted his workshops at Red- 
ruth, iu England, with gas obtained from coals, 
but it was not till twenty years later that the 
streets of Loudon were lighted by gas, and it is 
only within the last half century that this cheap 
and convenient means of lighting streets and 
buildings has come into general use. 
The most important product of the destructive 
distillation of coal is, of course, the illuminating 
gas, the manufacture of which has .already been 
described in these columns, ( July, 1888) ; but 
there are many by-products which are almost 
equally valuable. The residuum left in the retorts, 
known as coke, is a most excellent fuel, and in 
regions where soft coal is abundant, it is a regular 
article of manufacture, part of the resulting gas 
being used to heat the retorts, while the remainder 
is burnt or allo\\ed to escape into the air. The 
ammo'niacal liquor condensed from the hot gases 
as they come from the retorts contains no less 
than five different salts of ammonia, and is the 
chief source of supply of this inv.aliftible alkali. 
In all, there .are, at least, seventy different chemical 
compounds produced from the coal in the process 
of distillation, of which, perhaps, ten are useful 
as illuminating substances, while the remainder 
are either thrown away as impurities or saved for 
use in other ways. 
The most important of all the by-products is 
the coal tar, which was formerly thrown away, 
but is now almost entirely utilized. 'ITiis coal tar 
IS a black, viscous fluid, composed of about forty 
different hydrocarbon compounds. The discovery 
in 1858 of the aniline colors, first called attention 
to its value, and since then an immense number 
of chemical and medicinal substances, artificial 
flavors and peifumes, insectides, disinfectants, 
explosives, photographic developers, as well as 
four hundred or more different colors, have been 
obtained from an ill-smelling, repulsive liquid, 
which at first sight would appear to be the most 
useless thing on earth. 
Prominent among the substances contained in 
coal tar is a liquid known as benzol, sometimes 
less properly written benzene, as it is entirely 
different from the familiar cleaning agent known 
by that name. Benzol has the chemical formula, 
Cgllj, and is important as being the starting point 
or foundation stone, as it were, for a long list of 
compounds known as the aromatic series of hydro- 
carljons. To account for the chemical phenomena 
presented by the substance, it is supposed that 
the atoms forming the molecule of benzol are 
arranged in the form of a hexagonal ring, as 
roughly represented in the following diagram. 
Tlie lines connecting the letters represent the 
quantivalence or chemical affinities of the carbon 
and hydrogen atoms : 
H 
I 
II— C C— H 
II I 
II_C C— II 
H 
To tlioroughly explain the theory of the benzol 
ring, as it is called, would lead us too far into the 
mysterious realm of organic chemistry, and the 
above diagram is only given to roughly indicate 
the supposed structure of a single molecule of 
benzol. In all the innumerable derivatives from 
this substance, tlie inner ring of carbon atoms 
remains intact, but, by replacing the hydrogen 
atoms by other elements or radicals, both simple 
and compound, or by adding to the number of 
elements or radicals held to the ring by the carbon 
affinities, an immense number of substances may 
be obtained, some of which may be directly 
obtained from the tar, while others are produced 
in the laboratory from the benzol itself, and as 
the only important source of benzol is from this 
by-product of the gas works, a perusal of the list 
given below will show how much we owe to this 
