Gen. Roy’s Account of 
that their effects have almoft wholly difappeared. With regard 
to the deficiency of feven feet found between the a&ual mea- 
furement with the deal rods, on the Strand near Dunkirk, and 
the trigonometrical refult, it is necefl'ary to call to remem- 
brance what would have happened, if the bafe on Hounllov/ 
Heath had been meafured with our deal rods when in their 
greateft hate of expanfion from the moifture they had imbi 1 = d. 
In the volume of Philofophical Tranfa&ions for 785 p. 
438. it has been fhewu, that our bafe would thereby have bee 1 
rendered more than feven feet and a half too (hort. i aw, 
although the French rods were covered with feveral coats of 
oil-paint to prevent their imbibing the fait water, which we 
are told retted on the Strand at particular places fix inches 
deep ; yet it is prefumable, that it would be impoflible to pre- 
vent it from entering by the extremities at the jundion of the 
ferrules, and extending along the fibres, underneath the paint. 
Hence, in all likelihood, the intended remedy would prove 
worfe than the difeafe : for the paint might prevent the rods 
from dryinf fo foon as they otherwife would have done, and 
thereby the meafurement would be given ftill fhoitcr than it 
no paint had been applied. Whether this fuppofition may be 
thought to be well founded or not, is left to the determination 
of thofe who are converfant in matters of this fort. But the cu- 
rious fad, one way or other, might be afcertained by means of 
fuch a fteel chain as ours, in the fpace of one or two days 
at moft. For, fuppofing the extremities of the bafe between 
Fort Revers and the Dunes to be accurately known, and the 
alUgnement traced out on the Strand only with camp colouis, 
placed at reafonable diftances from each other, and a moveable 
cord, by the fimple application of the chain on the common 
furface, without any extraordinary apparatus whatever, for- 
, wards 
