1833.] and Dr. Gerard, from Péshdéwar to Bokhdra. 17 
method (at least with common thermometers, where the divisions which 
are so small, answer to so large an equivalent) is scarcely appreciable 
to the extent of 200 or 300 feet, which those land-locked seas are sup- 
posed to be depressed below the surface of the ocean. In this dry cli- 
mate, the horary variations of the barometer would amount to more 
than the above quantity, but we shall lose noopportunity of using every 
means to confirm so curious a conjecture, if it is not already settled. 
From the Oxusto Bokhara is more or less a desert tract, and the surface 
of the soil undergoes every modification of barrenness, from the hills just 
sprinkled with vegetation, to the hard-baked floor and dead sand heaps. 
The first four days no villages but camps of Turkmans were passed. 
The water was either salt or saliferous, and owing to our folly in trusting 
to information which is in its nature imperfect, as the springs of potable 
water are as variable as the sand hills, we suffered excessively from thirst, 
the sun raged with a burning heat, and we had no defence against it but our 
clothes. The wind of the desert dried* us like parchment, bnt the nights 
were cool, and often cold: this however did not take place till towards day 
break, and the few hours sleep we then got were deliciously refreshing, 
after heaving up and down upon a camel’s back all night. The face of the 
country was very uneyen, almost hilly; we at last came to waves of 
pure sand which were said to shift their position, like those in the 
African deserts, and we eagerly looked out for the moving heaps ; but all 
* “Tn the journey from the Oxus to Bokhara, the mean difference between the 
wet bulb and the temperature of the air was upwards of 20°, the extreme difference 
often 34° and 35°, and the least 10° or 11°, but in Calcutta during the same 
month (July) 3°.5 is the mean difference, and 5°. 5 and 2° the maximum and 
minimum.” At Benares, according to Prinsep, the difference between the wet and 
dry bulbs is sometimes 37° in the hot season. Bokhara seems to be drier in July 
than Calcutta is in January :—can July be the driest month at Bokhara, when the 
cold season appears to be driest in other parts of the world ?’ If the cold weather is 
driest here in winter, the evaporation must be astonishing, which will account for 
the excessive degree of cold in so low a latitude as 39° 43’. 
“‘ The evaporation from a cup can be easily measured by a scale: I found it 
more than once amount to two inches, in 24 hours, the thermometer being from 
72° to 104° in the open air ; in the shade, since entering Tarkistan, the highest has 
been 110°, and the lowest 54°, which occurred in the desert. In so arid an atmos~- 
phere you may suppose we do not complain of heat, although the thermometer 
is every day 97° and 98°in the house, and the more one perspires here the colder one 
becomes. It is owing to the hygrometrical state of the air, that we see icemade when 
the thermometer is above 50°, and by increasing the aridity, ice might be made 
at 70° : in fact a difference of 37° is nearly that in the driest months here, we ought 
therefore to expect ice with the thermometer at 80°. This great aridity will ac- 
count for the state of our feelings, the formation of ice, preservation of meat, drying 
of fruits, cold, vegetation, and many other phenomena.” 
D 
