268 BEPORT — 1844. 



Continental. Colonial. 



Milan. Toronto. 



Naples. St. Helena. 



Great St. Bernard. Cape of Good Hope. 



Geneva. Van Diemen's Land. 



Paris. 

 In the spring of the present year, the Honourable the Corporation of the 

 Trinity House allowed me most obligingly free access to the barometrical 

 records kept at certain lighthouses, and I obtained observations made at the 

 following stations : — Longstone, coast of Northumberland ; Heligoland ; Hais- 

 boro, coast of Norfolk ; St. Catherine's Point, Isle of Wight ; Scilly ; South 

 Bishop ; and Bardsey Island, coast of Wales. The plan I propose for tho- 

 roughly examining the wave is this : — 



I. To reduce all the observations to the level of the sea ; this I apprehend 

 is the only efficient test that can be brought to bear on the theory that the 

 non-periodic oscillations of the barometer are due to waves ; for if we con- 

 template a single wave, a barometer at the station over which the apex passes 

 at any given time, will exhibit a greater pressure than any of those at other 

 stations, and the slope to the other stations will be greater or less according 

 as they are situated on, or at any angle to, the transverse or longitudinal sec- 

 tions of the waves. 



II. To ascertain the difference of such reduced pressures between all the 

 stations, and to exhibit such differences on a diagram of the area over which 

 the stations extend. By this means I apprehend a more accurate idea can be 

 formed of the disposition of the atmosphere than the curves will afford, and 

 the highest and lowest points may be readily seen. As the lighthouse observa- 

 tions are taken every six hours, I propose constructing four such diagrams 

 for each day from the 8th to the end of November, and, as I find it neces- 

 sary; to colour certain portions of the areas indicating the progress of the 

 waves *. 



HI. When necessary, to construct models with a view to approximate to 

 the slopes of the waves, and particularly to mark the directions of the crests 

 and troughs, the maxima and minima. 



IV. With the assistance of the above-named diagrams and models, to pro- 

 ject sections of the waves taken in various directions, from which, should the 

 area be sufficiently extensive, the spans and altitudes may be approximately 

 deduced. 



V. To select the most advantageous lines from the area, and to project the 

 curves obtained at stations situated on or near such lines on the same sheet, 

 and referred to the same normal altitude, 29'500 for instance. The spaces 

 between each curve to be coloured, the same colour to be continually U7ider 

 the same curve. These coloured projections will indicate three things as con- 

 nected with the dispositio7i of the atmosphere; — 1st, the depth or extent of 

 colour will show the depression of the lower station below the upper ; 2nd, 

 the intersections of the curves will indicate that at the time of intersection 

 the stations had an equality of pressure ; and 3rd, the change of the position 

 of the same colour will point out that the station which exhibited or expe- 

 rienced the higher or lower pressure, afterwards experienced the lower or 

 higher, with its amount f. 



In this manner I have commenced the discussion of the observations now 

 in hand, and as the depression of the 1 1th November appears to be the com- 

 mencement of the large wave, I have thought it best to study the disposition 

 of the atmosphere over the area a few days previous, in order to obtain the 



* See Plate XLII. t See Plate XLIII. 



