266 On the Translation of Waves of Water. [No. 3, 



Length 5, wing 2 ^ tail 2. Bill ■£$, deep blackish brown with 

 pale tomia. Tarsus ^. Legs and claws deep blackish-brown with 

 yellow soles and tips to claws. The olive-green above is much the 

 same as in sylvicultrix, but the eye-streak and under-parts are much 

 yellower. 



On the Translation of Waves of Water with relation to the great flood 

 of the Indus m 1858. — By J. Obbakd, JH$q_. 



" At 5 A. M. on the 10th August, 1858, the Indus at Attock was 

 very low. At 7 A. M. it had risen ten feet. By 0.30 p. 31. it had 

 risen fifty feet, and it continued to rise until it stood ninety feet 

 higher than it did in the morning. The Cabul river continued to 

 flow upwards for ten hours. The fall was at first slow ; but the river 

 was about eight feet below its maximum by sunset ; and continuing 

 gradually to fall, it had during the 12th returned very much to the 

 position it occupied before the flood came down." — Extracts from 

 Journal of Asiatic Society, 1858, 1859. 



1. Several papers have been, recently forwarded to the Society 

 upon the great flood of the Indus in August, 1858, and, as it is a sub- 

 ject in which I take great interest, I trust that I may be excused 

 in submitting my views regarding it. 



2. I propose, therefore, in the following paper, to consider the mode 

 in which this vast body of water passed Attock, and with this view, 

 I shall first treat cursorily of the nature of waves of water generally, 

 more especially, however, dwelling upon waves of the class which from 

 their formation and size, seem to be analogous to that which is under 

 consideration, stating in general terms, their mode and rate of transit ; 

 and the limit within which wave translation is possible ; and I shall 

 then endeavour to shew the application of these laws to the speciali- 

 ties of the Indus wave, touching briefly upon some erroneous specula- 

 tions which seem to have been made upon insufficient data. 



3. A wave is an inequality of smface or variation of level in a 

 stream of water, which may be of any size according to the force of 

 its original cause. It is unnecessary to enquire into the origin of a 

 wave for the purpose of elucidating its specialities, as all waves when 



