548 
the Turner Mushroom System: H. T. Eppy, 
University of Minnesota. 
Owing to the apparently irregular distribution 
of the reinforcement employed in this system and 
to the uncertainty as to the value of Poisson’s 
ratio or lateral contraction for reinforced con- 
crete, engineers have differed widely in their esti- 
mates of the strength and stifiness of this form of 
construction, and have distrusted the results of 
tests made to determine deflections. The author 
has in this paper given a complete rational an- 
alysis of this form of construction and derived 
simplified but closely approximate practical for- 
mule for the resistance and deflection of this 
slab, showing how the various constants depend 
upon the properties of the materials composing 
the slab and how their arrangement affects its 
strength and rigidity. Of these several constants 
Poisson’s ratio is the most important. It is shown 
in the paper that the value of Poisson’s ratio 
obtained from experiments upon ordinary test 
specimens of square or round cross section is 
necessarily much too small for material cireum- 
stanced as is the reinforcement in a slab. The 
experimental results obtained from the deflection 
of mushroom slabs makes it probable that the 
proper value of Poisson’s ratio for the reinforce- 
ment is nearly twice that obtained from ordinary 
test specimens. On this basis the theoretical re- 
sults arrived at in the paper agree in a very 
striking and remarkable manner with the empirical 
formule which have been proposed to express the 
results of the numerous tests heretofore made on 
such slabs. 
The Primary Triangulation System of the United 
States; its Hautent and Uses: WILLIAM Bowie, 
U. S. Coast and Geodetie Survey. 
This paper shows that extended areas can not 
be accurately controlled by a number of discon- 
nected local trigonometric surveys, owing to the 
deflection of the vertical (or the station error) at 
the astronomie stations which control the positions 
of the several schemes of triangulation. The pri- 
mary triangulation, on the other hand, is continu- 
ous and no discrepancies will be shown between 
detailed surveys based upon it. The positions of 
objects shown on maps, charts and surveys based 
on the U. S. Standard datum will probably never 
be changed. Examples are cited of the use of 
trigonometric surveys by the United States and 
Canada Boundary Survey, by the state of Mary- 
land in its oyster survey, by the Isthmian Canal 
Commission, by the city of New York and by the 
SCIENCE 
[N.S. Von. XXXV. No. 90% 
Clinehfield Coal Corporation in Tennessee. It is 
planned to extend the primary triangulation into 
new areas as readily as possible, and it is hoped 
that, eventually, no place in the United States will 
be more than 150 miles from some primary station. 
Curved Line Vernier Method: H. E. WETHERILL, 
Philadelphia. Read by title. 
Differentiation of Satwrated Vapor Engines: J. 
E. SIEBEL, Chicago. Read by title. 
PAPERS ON THE WORK OF THE BUREAU OF MINES 
In Relation to Gas Producers and Internal Com- 
bustion Engines: R. H. FERNALD, Case School 
of Applied Science. 
The investigations show that practically every 
shipment of fuel tested in the gas producers, in- 
cluding coals as high as 44 per cent. ash, and 
lignites and peats high in moisture, has been suc- 
cessfully converted into producer gas which has 
been used in operating gas engines. It has been 
estimated that on an average there was developed 
from each coal tested in the gas producer plant 
two and a half times the power developed when 
used in the ordinary steam-boiler plant, and that 
such relative efficiencies will probably hold good 
for the average plant of moderate power capacity, 
though this ratio may be reduced in large steam 
plants of the most modern type. It was found 
that the low-grade lignite of North Dakota devel- 
oped as much power when conyerted into producer 
gas as did the best West Virginia bituminous coals 
when utilized under the steam boiler; and in this 
way lignite beds underlying from 20,000,000 to 
30,000,000 acres of public lands, supposed to have 
little or no commercial value, through these in- 
vestigations have been shown to have a large value 
for power development and the money value of the 
government’s own property has been increased to 
the extent of probably $300,000,000 or more. The 
investigations into the waste of coal in mining 
have shown the enormous extent of this vaste, 
aggregating from probably 200,000,000 to 300,- 
000,000 tons yearly, of which at least one half 
might be saved. It is being demonstrated that the 
low-grade coals high in sulphur and ash now being 
left underground can be used economically in the 
gas producer for power and light and should, 
therefore, be mined at the same time that the high- 
grade coal is being removed. The use of these 
low-grade fuels, which have previously been re- 
garded as of little or no value, increases our fuel 
resources approximately (on the basis of present 
marketable grades): low-grade bituminous and 
anthracite, 75-100 per cent.; sub-bituminous, lig- 
