166 J. D. Dana—Results of the Earth's Contraction. 
These iron-bearing kinds of Archzan metamorphic rocks 
much exceed in amount the granitic kinds that are free from 
iron. Moreover, in these Archean formations, the granitic as 
well as the iron-bearing, there are immense beds of iron-ore, as 
seen in New York, Canada, Northern Michigan, Missouri, 
iron age was its earliest. Now since these great iron-ore beds 
are of sedimentary or marsh accumulation (for they occur inter- 
stratified with quartzite, chlorite schist, syenitic schist, and 
other metamorphic rocks), the iron was gathered from the pre- 
existing crust: rocks. They therefore prove that iron was 4 
very common ingredient in the original fused material of the 
surface of the liquid globe. 
(f) We hence have reason for the inference that the 
original fused material contained largely the ingredients of 
the iron-bearing rocks, dolerite, peridotite, diorite, hyposyenite, 
besides trachyte and the balaton kinds; and perhaps in small 
proportions those of the quartziferous trachytes, if not of 
granite and syenite. 
t is not certain, from present knowledge, whether the slow 
made 1 
