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VII. — On the Advantage and Use of the Anei-oid Barometer in 
ascertaining Heights. By Nicholas Whitley. 
The physical features of all countries greatly influence the pro- 
ductions of the soil ; chiefly in goveining the climate of the 
lands situated at various elevations, but also in respect of the 
facility afforded for irrigation, and the means for the transit of 
produce. 
So conscious are most agricultural writers of this fact, that a 
description of the agriculture of any distiict is generally prefaced 
by a sketch of its physical geography, often too meagre and 
indefinite. This defect arises in most cases from the difficulty of 
obtaining the relative heights above the sea of the various pio- 
minent points of the district. The operation of levelling even 
with the favourite " Dumpy " is slow and exjiensive, and requires 
a practised eye and a previous training. 
The object of this paper is to point out a simple and rapid 
mode by which the relative heights of a country may be ascer- 
tained, and described with sufficient accuracy for all agricultural 
purposes. 
The mercurial barometer has long been applied to the measure- 
ment of altitudes, but the newly invented Aneroid Barometer is 
at once so cheap, portable, and practical, can be used with such 
facility, and with such comparative accuracy in the results, that 
it offers the most ready and expeditious method of obtaining the 
relative elevations in order to an accurate description of the 
country. 
I was enabled in a day's travelling by coach and rail to de- 
termine the chief elevations of the land from Truro to Plymouth, 
Exeter, Wellington, and the Blackdown hills ; and on the 
following days, of the high lands of North Devon and Exmoor ; 
and this without any additional labour or expense, but by obser- 
vations which tended to relieve the tedium of travelling. 
I am induced, therefore, to recommend the use of the Aneroid 
to those who may hereafter describe the features of any district, 
and I shall here venture to give the result of my experience with 
this instrument for their guidance. 
The datum should in all cases be the mean level of the sea, 
or some point above it whose height is known ; as a railway 
station, canal lock, surveyors' bench-mark, &c. 
The instrument should be kept as near as may be at the same 
temperature, read with the dial horizontal, first at the datum, 
then at the several points where the heights are required, and 
again on returning to the datum to ascertain if there has been 
any alteration in the atmospheric pressure ; if so, it must be 
distributed over the stations in accordance with the times of 
observation. 
