96 
materially in facilitating the arrangement of the formalities for 
clearing and entering our material without detriment to the 
collections 
The entire delta of the river was practically flooded and our 
descent was so arranged ‘that stops were made only at the three 
places in which the main channel cuts directly into -_ Sonora 
Mesa known locally as “the Upper Mesa,” ‘‘the Middle Mesa,” 
and “the Colony Mesa.” <A delay of two days was cere 
at the last stop by a sandstorm, and occasion was taken to trace 
the channel of the Santa Clara Slough which connects the river 
directly with the Gulf, to adjust the instruments and calculate 
the occurrence of the tides in the lower reaches of the river, a 
matter of great importance to an expedition of this character. 
A minute examination was made of the desert here to ascer- 
tain - ee of the et rainfall of the two months previous, 
and while some increase in the number of a few annuals such as 
asmall Astragalus, an ee anda Krynitzkia, yet the increase 
was hardly so marked as in the sloping mesas which had been 
examined three hundred miles to the northward. The flooding 
of the sloughs and shallow channels in the ‘delta had given 
pre for the hatching of m s of mosquitoes and these 
only swarmed around our ae oe had been carried out 
across the sandy mesa for many miles and constituted a serious 
annoyance in the investigation of these desert areas 
Before leavirig cainp near Colonia Lerdo a Cucopa Indian, 
Miguel Gonzalez was added to our party. On April 1 we 
dropped down the river to a point on the western shore a few 
hundred yards below the mouth ei Hardy’ s Colorado and made 
camp for a day ona flood-plain bearing salt-grass, Cressa and 
mesquite, and which is inundated by the bore at spring tides, 
Here we found that the water had spread from the delta across 
to the low plains west of the lower part of the river and was 
pouring off the banks in numerous cascades extending for many 
miles up and down stream and making a deafening roar in places. 
We waited here for a day, taking observations to locate the exact 
position of the mouth of the Hardy which does not appear cor- 
rectly on any published map, and also to time our movements 
