415 
comparatively small expense. But in one important particular they fall short of the 
requirements of a qierfect boring tool. It is impossible to obtain a record, of the sti’ata 
cut through. Had such a record been obtained, and systematically preserved, there 
must have been by this time an accumulation of data invaluable for the purpose of 
directing and economising future operations. Owing to the manner in ■which the 
material is pounded up, the strata of one boro can never be “ read ” with those of 
another. All that it is open to us to record is the depth at which artesian water has 
been met with in various localities, and with this, for the present, we must rest content. 
I append to this Chapter, for reference, such records as have reached me on the subject. 
Brom this record it will bo observed that in some cases artesian water has been 
met with at comparatively shallow depths in the vicinity of springs, aud for the most 
part in the vicinity of thermal springs. The subjects of artesian water aud thermal 
springs have evidently an intimate connection. 
To begin with thermal springs, the first thing we discover is how extremely vague 
mid unsatisfactory are the explanations offered by the best authorities. The whole of the 
light hitherto thrown on the subject maybe summed up in the following quotation from 
Dr. A. C. Beale’s Eeport on the Thermal Springs of the Yellowstone National Park * 
" Everywhere that observations have been made, there appears to be an increase (of 
temperature) as we descend towards the centre of the earth. In this increase of heat, 
ef course, we have sufiicient reason for the heat of springs coming from a great depth. 
■In many thermal springs, however, as in our Yellowstone Region, this regular increase 
m temperature is not sufficient to account for the high temperature, and we must look 
for the cause in plications and faults or in the volcanic rocks in which the springs are 
located.” 
Rocks of igneous origin (c.y., basalts) may, and in some cases must, still retain 
at comparatively shallow depths enough of their original heat to raise the temperature 
cf any w'ater with which they may come in contact to what is usually understood by the 
boiling-point— ^■.e., the boiling-point under the pressure of one atmosphere. But the 
Contact must take place at depths so shallow that the pressure of suprajacent water or 
I'ock shall not raise the boiling-point of water above the temperature of the rock. 
Every lava-flow which appears at the surface must be connected with underground 
ramifications, consisting essentially of a “ reservoir ” and a channel. The material in 
both reservoir and channel must, at least in the case of all but very recent eruptions, 
be consolidated ; but rocks of the lava class arc very bad conductors of heat, or, in other 
^ords, part with their original heat very slowly. The connection of hot springs in aU 
parts of the world with recent or, geologically speaking, not very ancient volcanic rocks, is 
How well known. 
Careful observations have shown that, so far as the investigations could be 
‘tarried, the internal heat of the Earth increases about 1° Fahrenheit for every fifty or 
sixty feet of depth, and it might be thought that, from this cause alone, -n'lierever water 
®ouid penetrate to sufficient depth it would be boiling, but this can easily bo shown to 
be an error. Assuming an increase of one degree in fifty feet, aud the surface tem- 
perature to be seventy degrees, a depth of at least seven thousand one hundred feet 
'^ould have to be attained before the rock forming that portion of the earth’s crust, or 
'vater in contact with it, would have a temperature of 212°. Nevertheless, a column of 
'vater reaching from the surface to a depth of seven thousand one hundred feet would 
hy any means have its base at the boiling-point, because the boiliug-pomt of water 
raised enormously by pressure. From observations made at the tireat Iceland 
* Twelfth Ann. Iteport IT. S. Geol. Googr. Survey of the Territories for 1878, Pb. 2, Washington,1883. 
