172 H. JV. Pearson — Oscillations of Sea-level. 



rising, and as I knew they were falling in England, Italy, and 

 France about 1500, my conclusion was that somewhere between 

 these dates, say from 1450 to 1475, I must expect to find the 

 culminating period of that particular epoch of northern submergence. 



From this preliminary examination I was led to believe that 

 a high-water period must certainly have existed over the greater 

 portion of the European shores, culminating not far from the year 

 1450. I therefore entered upon a more extended search for data, 

 not only as to this particular epoch of an elevated sea, but for those 

 ■other and more ancient changes which I had been led to suspect 

 as stated. 



For many years I pursued this search, carefully collecting and 

 indexing every notice as to change of sea-level encountered in my 

 readings, regardless of date or direction of movement. The data 

 thus accumulated seem to me conclusive ; periodic vibrations in the 

 ocean level are certain beyond question. The present cycle appears 

 to have a period of about 640 years, while the evidence points to 

 a period of about 500 years only at about the time of the Christian era. 



A portion of the data which have been used in establishing this 

 curve (see Diagram, next page) is submitted herewith. Hundreds, 

 however, of the facts used as ordinates are omitted, that this paper 

 may not be swollen to unreadable size. 



When this material had been mapped out, it was found that 

 -300 points or more were aggregated in a compact body, central 

 about the year 1475, and that each of these points bore testimony 

 to a period of high-water at some part of the earth's surface north 

 of the Equator ; another aggregation of points, less numerous and 

 each one indicating a low-water period, was found bunched between 

 the years 1100 and 1200, central about 1150 to 1175. I thus laid 

 out all these accumulated facts each in its pi'oper place and position, 

 and at the end found a dense haze of dots central about the years 

 825 and 325 a.d. and 250 B.C., these clouds representing high-water 

 periods, and similar swarms of dots, each representing proofs of low- 

 water, central about the years 600 and 100 a.d., with occasional and 

 conflicting points, scattered indiscriminately along the line. 



At this point, then, to complete my curve it was but necessary 

 to draw a sinuous line through these preponderating masses of dots ; 

 this curve was drawn, and the result is shown in the accompanying 

 Diagram. 



I now examined as to what weight these conflicting points might 

 have towards weakening my confidence in the general accuracy of the 

 curve. Much labour has been given to this subject ; many of these 

 dots were removed by investigation, others I attribute with good 

 reason to erosion of shore-lines or to accretion to shore-lines, as is now 

 going on all over the world, and finally I decided that not one of these 

 ■conflicting points could be depended upon as making serious objections 

 to the correctness of our curve. The information was too uncertain 

 in its nature; it lacked that element of the positive, the known, 

 which pervaded the great mass of evidence on which the curve had 

 been based. 



