490 A, E. Verrill—The Bermuda Islands. 
between the reefs. Ordinary tides rise from 34 to 4 feet, but the 
spring tides may rise 5 feet, and in gales of wind sometimes 7 feet. 
In Harrington Sound there is usually only 6 to 8 inches of tide, seldom 
a foot. Near the shores the tidal currents run in various directions, 
often varying according to the winds. 
In 1666, the Royal Society of London (founded in 1662) sent to 
Mr. Richard Norwood, the surveyor, a long series of questions con- 
cerning these islands and their productions, whale fishing, ete. 
Many of these were answered in a letter from Mr. Richard Stafford 
(later Judge Stafford), July 16, 1668. Mr. Norwood replied to the 
questions concerning the moon and tides, in a letter of June 18, 1667. 
Both letters were published in the Philosophical Transactions, vols. 
it, 
In his letter Mr. Norwood gives several facts as to the tides. He 
stated that the tides commonly rise 4 feet, at spring tide 5 feet, but 
that they are variable according to the wind ; in calm weather the 
flood tide sets from the southeast ; high water occurs at 7 o’clock 
on the “change day.” 
16.—The Soil ; its Origin and Composition. 
With the exception of the black peat or muck of the swamps and 
marshes, all of the soil of the islands has been produced as an insolu-’ 
ble residue, or impurity, left after the solution of the limestones and 
shell-sands of the islands by rain water, but it is usually mixed with 
more or less disintegrated limestone, and some organic matter. 
These rocks and sands always contain a small amount of earthy 
impurities, often not more than 0.5 of one per cent., and seldom more 
than one per cent., which consists mainly of clay and iron oxide, and 
with a little phosphate of lime, potash, etc., to which the soil owes 
its fertility. 
This process of forming soil is a very slow one, and indicates, as 
well as anything else, the long period of time that has elapsed since 
the Bermudas became dry land. The average thickness of this soil 
has been variously estimated at from one to two feet, which would 
require the destruction of at least 100 to 200 feet of limestone. (See 
under Geology.) 
Where the decomposition has been complete, this soil is a reddish 
clay, the color being due to an excess of iron oxide, but in most 
places the clay soil is mixed with considerable shell-sand, or grains 
of undecomposed rock. In many places the latter forms the greater 
