29S ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



cone or Nnmmulitic in age. The beds of salt, more or less 

 mixed with clay, have an apparent thickness of 1000 feet, 

 and are overlaid by gypsum. To the east of the Indus, south 

 of the Tertiary plateau of the Punjaub, and separating it from 

 the great alluvial plain lying to the southward, rise, for 150 

 miles, the hills of the Salt Range. These include Nummulitic 

 and Carboniferous rocks of marine origin, below which is a 

 horizon of dolomites and sandstones without fossils, resting 

 conformably upon a layer of 200 feet of dark glauconitic 

 shales, which have yielded two species ofObolus. Below this 

 is a thick group of dull-purple sandstones and conglomeratic 

 shales, becoming earthy in its lower part, and passing down- 

 ward into the red marls of a salt-bearing group, which is 

 found for a Great distance alono* the southern foot of the 

 range. It has an estimated thickness of 1000 feet, of which 

 the upper half consists in large part of rock-salt, with layers 

 of clay and thick beds of gypsum, the latter sometimes hold- 

 ing crystals of quartz and of pyrites. These beds are accom- 

 panied by small intercalated masses of what is described as 

 a purple volcanic rock, with crystals of actinolite, the only 

 evidence of eruptive action observed in the range. In one 

 locality the marls contain a small lenticular deposit of syl- 

 vine (chloride of potassium), with kieserite, as in the Mesozoic 

 salt formations of Central Europe. The precise age of this 

 very ancient salt formation is uncertain, but it is called by 

 Wynne Cambro-Silurian. It is to be noted that Hunt has 

 pointed out that some of the conditions of a salt formation 

 existed at an early period in the American Paleozoic series, 

 as is shown in the strong brines or bitterns which, in several 

 parts of the St. Lawrence valley, rise through the Trenton 

 limestone, and in the presence of small masses of gypsum in 

 the underlying dolomitic formation known as the Calciferous 

 sand-rock. The presence of salt deposits, as he has explained, 

 shows the existence, at the time and place of their formation, 

 of geographical and climatic conditions favorable to the evap- 

 oration of sea-water. 



It is to be remembered that the great salt and gypsum de- 

 posits of Eastern North America are Paleozoic, and occur in 

 part at the base of the Carboniferous (in which they are found 

 over various areas from Colorado to Nova Scotia and New- 

 foundland), and in part in the upper portion of the Silurian, 



