Normandy, no doubt enables a fortress placed there to command the approach to the adjacent land; but the peculiar run of the tide, the vast extent of sand at low water, and the innumerable rocks further out at sea, are natural defences, superior to any that can be placed there by man. The English certainly ought not to complain because their neighbours endeavour to make the most of the very few and small advantages they possess in these islands, when we consider the far greater importance and accessibility of the British possessions in the Channel. Alderney is not further from the French coast than the 'Grande Ile' of Chaussey; but the one island is so placed as to command a great and wide channel through which a large proportion of the whole commerce of the world must pass, while the other is only approached by a few small and unimportant vessels, for it leads nowhere, and can threaten nothing.

The subjoined illustration represents an abandoned ship laden with teak, wrecked in the Channel and seen drifting towards the Douvres rocks, in the winter of 1861.

CHAPTER VII.

CLIMATE AND METEOROLOGY OF THE ISLANDS, AND THEIR SANITARY CONDITION.

THE geographical position of the Channel Islands indicates at once to the physical geographer, the peculiarities that are likely to be presented in their climate, and in the meteorological phenomena to which they are subjected. Placed near the western extremity of the European continent in a wide channel, communicating without interruption with an open ocean; situated not far from the main land, but within the influence of a group of much larger islands; enclosed within a large bay, of which a part of the group forms one of the horns, and whose form greatly influences the tidal wave-these conditions suggest causes of local climate, well worthy of consideration, and all pointing to one conclusion.

In the first place it must be mentioned as an ascertained fact, that near as the islands are to each other, to France and to England, their climates are in essential points distinct and local, and need separate consideration. We should, therefore, consider the peculiarities of one typical island, and then compare this with the others.

Guernsey, from its position as the outlying island—the most completely in the centre of the Channel-the furthest removed from land-of medium size and of medium elevation, compared

THE CLIMATE OF GUERNSEY TYPICAL.

133

with the other islands-must be regarded as typical in respect of climate.

To be satisfied that this is the case, the reader need only refer to the physical map at the end of this volume, and consider the relative positions of all the islands and the nearest land. Alderney is within seven miles of France, and has an important group of rocks protecting it from the west. Jersey is double the size of Guernsey, only half the distance of the latter island from France, and is more in the heart of the great bay. Sark is very peculiar in its extreme smallness and the near approach made by its surface to a level, lofty table land; but as respects climate, it must receive the westerly winds after they have left Guernsey, and the easterly winds before they reach it; thus, in every sense, rendering Guernsey the typical island.

Under these circumstances, it cannot but be regarded as eminently fortunate, that since only one of the Channel Islands has had the advantage of systematic observations, extending over several years, this island should be Guernsey; and in referring to the annexed tabular view, it is satisfactory to be able to direct attention to it as containing a near approach to absolute results. The period of observation does not include the years since 1858, inasmuch as they have been exceptional in many respects, and probably form part of a cycle not yet completed, whilst the sixteen years selected appear to complete two climatal cycles.

N.B. The instruments employed in making the observations from which the table is constructed were as follows:-(1.) Barometer; made by Henry Barrow; compared with the standard by Mr. Glaisher. (2.) Thermometers; dry and wet bulb and maximum instruments made by Negretti and Zambra, index error determined by Mr. Glaisher; minimum thermometer made by Newman, on Rutherford's construction; all four feet from the ground, and many yards from other objects. Wet and dry thermometers read at 9 a.m. and 3 p.m. Minimum and maximum, at 9 a.m. Corrections for daily range applied from Mr. Glaisher's tables; barometer correction for elevation above sea level not applied. (3.) Rain Gauge; a copper funnel and cistern; the contents measured by a graduated glass jar. Instrument twelve feet from the ground, and quite free from the influence of trees and buildings.

Range of barometric readings
Mean temperature of air-corrected
Mean temperature of dew point
Mean dryness-thermometric scale
Mean humidity-hygrometric scale
Highest readings of max, thermom.
Lowest readings of min. thermom.
Mean monthly range of temperature
Mean daily range of temperature
Amount of rain collected..
Number of days of rain, hail, or snow.
Mean amount of cloud

877 8591 857 836 ⚫861 .848 827 .868 8.50

MEAN ANNUAL TEMPERATURE OF GUERNSEY.

135

The elements of climate may be considered to include the distribution of heat through the different days, months, and seasons, the variations of the pressure of the air as indicated by the barometer, the direction and force of the prevailing winds, the quantity of rain-fall and its distribution through the year, the dryness or moisture of the air from time to time, and the electric state of the air. To understand these fully, it will be necessary to refer to each in some little detail.

And first with regard to temperature. It will be seen from Dr. Hoskins's table, that the average annual temperature of Guernsey is 51°, and the following diagram will show how little this varies from year to year, and will also point to a significant fact, namely, that there has been during the period of observation one cycle of five years, during which the temperature was higher than the mean, succeeded by another cycle, also of five years, during which it was lower. We appear now to be entering a third cycle, which promises to be exceptional. The cycles of temperature do not thus appear to correspond exactly with the cycles of general climate.

Illustrating the range of the mean annual temperature at Guernsey,
from 1843 to 1858 inclusive.

In the diagram, the middle line, 5140, marks the absolute mean, and the waved line, ranging above and below it, the actual mean of each year of the sixteen. The positions of the means of 50 and 53° (the extremes) are each indicated by a broken line.

The adopted mean temperature at Greenwich being 49°, it is evident, that on the whole, the climate of Guernsey may be regarded as 24 warmer. This, though itself a considerable increment, gives little idea of the nature or extent of the whole difference that exists between the two stations. In order to