Marcu 17, 1923] 
carbonisation-amount to 10 million tons of coke, 
180 million gallons of tar, 170,000 tons of sulphate of 
ammonia, and 45,000 tons of sulphur annually. About 
87 per cent. of street lamps in the country are lit by 
gas. The annual make of gas is approximately 1200 
million therms supplied to consumers through about 
8 million meters. The figures are clamant for the 
- maintenance of a due sense of proportion in criticism 
of the industry. We commend them to the notice 
of any inclined to regard the gasworks as the original 
home of the three-card trick, and the gasometer as 
the present-day residence of the Borgias. 
Mr. Evetts has produced an extremely clear and 
readable account of the legislative and adminis- 
trative aspects of the gas industry. Primarily in- 
tended to meet the requirements of the student, the 
junior assistant, and others desirous of qualifying for 
high administrative posts in the industry, the book 
will be welcomed by a much wider circle of readers. 
The provisions of the Gas Regulation Act, 1920, 
enabling gas to be supplied and sold on the basis of 
its potential thermal value, are set out in Chapter 2. 
Although from the date of the publication by the 
Board of Trade of the brochure on Gas Standards 
the gas industry generally welcomed the suggested 
new method of supply (p. 34), it should be remarked 
that at a somewhat earlier date such suggestions 
were regarded favourably only by a very small minority 
of representatives of the gas industry considering the 
subject. The supply and sale of gas on the only 
conceivable scientific basis, namely, on a thermal 
basis, having regard to present-day uses of gas, we 
owe to the Board of Trade. The electrical unit of 
energy supply is termed the Board of Trade Unit. 
We suggest that correspondingly the unit of supply 
of gaseous energy should be designated the Board 
of Trade Therm. 
Among the matters dealt with by Mr. Evetts are: 
the sliding scale of gas charges, parliamentary pro- 
cedure when applying for a Bill, the model Bill, repairs 
and depreciation, hirings and fittings, arbitration and 
other workaday matters. Chapter 8, dealing with 
financial aspects of the sale of gas by therms, is a clear 
statement of the numerous facts to be taken into 
consideration before a calorific value is declared. 
Advocates of the supply of low-grade gas should 
ponder well the tables on p. 242, giving the costs of 
mains and the pressures necessary to deliver a definite 
quantity of energy in the form of gases of various 
calorific values. In this connexion we may remark 
that such changes in declared calorific value as have 
recently occurred have all been in the direction of 
supplying gas of higher calorific value. 
(2) Dr. Weyman’s book on modern gasworks 
NO. 2785, VOL. 111] 
NATURE 
351 
chemistry describes the methods employed in the 
control of plant and processes employed in the manu- 
facture of towns’ gas. Chapters are devoted to coal, 
carbonisation, coke, refractory and insulating materials, 
tar, ammonia, oxide purification, steam raising, water 
supply, and lubricants. A great amount of work has 
gone to the collection of the very large number of 
analytical and other tests comprised in the volume 
We regret that frequently these are not sufficiently 
detailed or clearly described to afford working instruc- 
tions. Occasionally, and more especially in regard 
to what would be regarded as essentially physical 
tests, the descriptions are inaccurate or meaningless. 
As examples, we would refer to the calorimetric radia- 
tion correction (p. 27), the standardisation of the 
Wanner pyrometer (p. 56), and the determination of 
thermal conductivity (p. 74). It is certain that the 
methods described for the determination of the thermal 
conductivities of materials will not yield results of 
much value in the hands of the works chemist. This 
class of work should, we think, for the present, until 
the gas industry is equipped with its own large central 
testing establishment, be allocated to the National 
Physical Laboratory. In any case, if this section of 
the book is to be retained in later editions, it should 
include a description of the simpler flow methods, 
developed at the National Physical Laboratory for the 
determination of thermal conductivity, and probably 
more suitable for adoption in industrial laboratories. 
(3) Dr. Levy’s work on gasworks recorders is the 
complement of Dr. Weyman’s. Control of chemical 
processes can be based upon the results of snap-tests 
or the indications of recording devices. There is much 
to be said for both methods. Painful experience with 
some recorders forces the present writer to the un- 
fortunate conclusion that generally the former method 
is to be preferred to the latter. Individual observers 
suffer from their “ personal equations.’ Recording 
devices are not without their idiosyncrasies. Their 
value and trustworthiness are to be determined by 
the “acid test’: How far is the record influenced 
by, and only by, variation in the characteristic to be 
recorded ? Frequently the influence of disturbing 
factors, such as friction, temperature, and the rest, are 
completely overlooked in the design of such instruments. 
Pressure and vacuum gauges, pyrometers, gravito- 
meters, gas analysis and volume recorders, and densi- 
meters are among the recorders discussed in this volume. 
The activity, born of the Gas Regulation Act, 1920, 
among makers of scientific instruments is evidenced 
by the chapter devoted to recording gas calorimeters. 
Prof. Boys’s instrument, incorporating many novel 
features and points of geometric design, is worthy of 
the close attention of scientific instrument makers 
