102 On Wheel- Carriages 
When we turn our attention to ether, we find the discre- 
pancies, if possible, less easy to reconcile. At the temperature 
of 212°, for example, where the old and new scales meet for the 
last time, the force of its vapour by the geometrical progression 
exceeds that found from experiment, by the enormous quantity 
of 67 inches and a half; amounting to two-fifths of the whole 
elastic force evolved. 
May we venture, then, to conclude, from these multiplied com-_ 
parisons, that the progressions of elasticity in vapours, taught by 
Mr. Dalton, are geometrical fictions, intended to quadrate with 
his notions concerning temperature; but not consonant with the 
laws or phenomena of nature? 
Within a moderate compass, indeed, it is not difficult to suit 
the ratio of elastic force and the thermometric graduation to each 
other; but the prosecution of the inquiry into ranges more re- 
mote, detects the fallacy of such hypothetical adaptations. My 
experiments on the vapours of water, alcohol and ether, seem to 
show, that the ratio of tension decreases in a certain progression 
as the temperature augments. Were the ratios 1:23, 1:22, 
1:21, &c., which are seen to apply so well to aqueous vapour for 
a considerable range above 212°, to be adopted as representing 
the progressive march of nature, it would lead to the absurd con- 
clusion, that at 240° above the boiling point, or 452° F., the 
further influx of caloric would occasion a diminution of elasticity 
in the steam. The truth however is, that at the 312th degree, 
indications of a divergence begin to appear between the two lines 
of experiment and calculation, which had run for so long a space 
nearly parallel. The curve representing the expansive force of 
steam, I consider to be logarithmic, in which the ratios, as or- 
dinates, continually diminish, without ever vanishing, or coming 
to an equality. The axis is an asymptote to the curve, as in the 
atmospherical logarithmic. 
[To be continued. | 
XVI. On Wheel-Carriages and their Effects upon Roads. By 
Mr. Jouy Farry Sen. Mineral Surveyor. 
To Mr. Tilloch. 
Sir, I AM glad to see the important subjects of Wheel-carriages 
and Roads, brought under the notice of your readers, by the 
communication of Mr. Benjamin Wingrove, in your last Number ; 
wherein he recommends two important improvements; viz.to pre- 
vent or lessen the evils of dragging waggon wheels down the hills, 
and the constructing of curriages of an uniform breadth, so that 
their wheels repeatedly follow in the same tracks, and cut ruts i 
the 
