ON FUEL ECONOMY. 943 
Hourly Heights (feet). 
Average Maximum 
error error 
R-machine .. ...  Tising tide — 0:24 —047 
falling ,, —0'06 
N-machine... ae | TISINE: + ,, -0:15 0:45 
falling ,, —0:09 
These tests indicate :— 
(1) that both machines have zero errors in height, that of the R-machine being 
serious ; 
(2) that both machines have serious time errors averaging about 6 minutes ; 
(8) that the throw of the machines (or apparent range of tide) is deficient, 
but not seriously so; 
(4) that the machines have no produced predictions with tbe accuracy 
required in research work. 
The average (or zero) errors are easily allowed for, even if the machines are not 
mechanically adjusted, There are certain other errors which may be serious, e.g. 
the variation of the H. and L.W. time error from two to thirteen minutes in one day— 
apart from the zero error the performance of the R-machine is more creditable than 
that of the N-machine in this respect. 
The tests have been made with the machine scales used commercially. The time 
scale could be altered if greater accuracy were desired. It may be stated that 
six mins. is represented by one-fortieth of an inch on the chart and that this is the 
average error with very careful reading. 
Both machines agree better with one another than with calculations ; but they 
are of the same type and were built by the same maker, so that it might be expected 
that similar faults would be present. 
The above tests ought, perhaps, to be supplemented by others in which the 
machines are more fully used ; the present tests have only used five constituents out 
of the twenty or ihirty represented on the machines. 
In connection with methods of research (Part IL) it may be remarked that the 
machines would have been useless for the purpose covered by the scheme for 
prediction (§ 12), and the labour of reading the curves with any pretence to accuracy 
is quite comparable with the labour of direct numerical calculations, but the results 
are not comparable in value. 
Fuel Economy.— fourth Report of Committee appointed for the In- 
vestigation of Fuel Economy, the Uiilisation of Coal, and Smoke 
Prevention (Professor W. A. Bonu,* Chairman; Mr. H. James 
Yates,* Vice-Chairman; Mr. Roserr Monp,* Secretary; Mr. 
A. H. Barxer, Professor P. P. Brpson, Dr. W. §. 
Bourron, Mr. E. Bury, Professor W. E. Datsy, Mr. 
K. V. Evans,* Dr. W. Gantoway,* Sir Rospert Hap- 
FIELD, Bart.,* Dr. H. S. Heue-Saaw,* Mr. D. H. Hates, 
Dr. G. Hicxuine, Mr. D. V. Howiinawortu, Mr. A. 
Horcurson,* Mr. S. R. Innincworrs, Principal G. Knox, Pro- 
fessor Henry Lovis,* Mr. H. M. Morcans, Mr. W. H. 
Patcuetn,* Mr. A. T. Smrrx, Dr. J. E. Sreap, Mr. C. E. 
Srromeyer, Mr. G. Buaxe WatLKER, Sir JosepH Watton, M.P.,* 
Professor W. W. Warts,* and Mr. C. H. WOoRDINGHAM*). 
Norz.—* Denotes a member of the Executive Committee. 
Ow1ne to two unforeseen causes, namely (1) the unprecedentedly difficult and 
anxious industrial situation during the past autumn and winter, accentuated, 
as it was, by the stoppage of the coal mines in October last, and culminating in 
the great coal-strike of this year, and (2) the sudden and serious illness of the 
