120 REPORT—1845. 
onthe 10th and 24th, with an interval of fourteen days; the semi-interval would 
give the included minimum onthe 17th. Upon the assumption that the crest 
of the normal wave passed the stations on the 24th, the preceding crest having 
passed on the 10th, we have the normal trough passing on the 17th: the 
numbers in Table V. appear to indicate a gradual rise and fall preceding and 
succeeding the highest reading of the 24th, such as might be expected from 
the transit of a large wave, the anterior and posterior slopes being indented 
and masked by the transits of smaller waves flowing in various directions. The 
numbers and directions in the table convey the idea of a certain regularity 
in the flowing of these secondary and superposed waves. During the transit 
of the normal wave three systems of waves appear to have traversed the area 
included by the stations, from W.N.W., S.W. and 8.S.W. The crests of the 
latter system (3 waves) were only observed, but the intervals being so nearly 
equal, induces the opinion that they succeeded each other with great regularity, 
and were accompanied with troughs, although those troughs were masked and 
concealed by the other systems. It is also probable that the altitudes of these 
waves were nearly equal, the apex of the central wave being elevated by that 
of the normal. The W.N.W. system appears to have been a system the 
waves of which were increasing in size; the altitudes do not appear to have 
been sufficiently high to have occasioned them to ride above the upper por- 
tion of the normal wave. The waves of the S.W. system were rather larger 
than the earliest W.N.W. wave. 
If we consider the low readings of the 18th to mark the anterior trough of 
the normal wave and the maximum of the 24th to indicate its crest, we have 
the following elements and co-ordinates. 
TABLE IX.—Normal Wave. 
Anterior Trough, Crest. Co-ordinates. 
Station. Ep sen a Tt Altitude. pene Teeit, Altitude. || Altitude. | Semi-interval. 
d hj} Eng. in. d h{| Eng. in. || Eng. in. hours. 
Greenwich .|March 17 18] 29501 |\March 24 0} 30-329 f 150 
Munich ..... » 18 4| 30-103 |} , 23 29] 30-667 || 564 138 
Prague...... + 18 4) 30-009 _ 25 8) 30-400 |, -391 172 
The close of Table V. gives the lowest reading for the period included by it, 
and did not the barometer continue to fall, we might consider this point as the 
posterior trough of the normal wave. ‘The following are the altitudes of the 
wave from this point, with the semi-intervals. 
Station. Altitude. |Semi-interval. 
Eng. in, hours, 
Greenwich ....| °733 208 
Munich ........ 783 230 
Prague.,....... 726 194 
It is clear that the above elements of the normal wave, as well as those of 
the superposed or secondary waves, are greatly modified, the first by the 
secondary waves, and these again by the normal wave, and by each other. 
There is great reason to believe that the troughs of the S.S.W. waves were 
concealed. It will be shown in another part of this report, that by compa- 
ring observations at two stations and examining their barometric differences, 
the passage of a crest or trough may be rendered apparent, which by this 
mode of investigation remains concealed. Nevertheless it is highly probable’ * 
ae 
