March 2, 1883.1 



SCIENCE. 



91 



nels and basins which hold the coal, composed 

 of the Waveiiey shales, or the carboniferous 

 conglomerate. 



From these facts I translate the following 

 history, which I am sure will be accepted as 

 true by every geologist who has had sufficient 

 experience in field-work to make his judgment 

 of such phenomena trustworthj'. 



I. At the beginning of the formation of the 

 coal-measures, north-eastern Ohio was a land 

 surface, underlain by the Waverley shales, or 

 beds of gravel, now the conglomerate. This 

 surface was furrowed b}' the vallej's of streams, 

 and pitted by local basins, similar to those 

 which mark the present surface. 



II. With a .slow subsidence, which con- 

 tinued with interruptions throughout the coal- 

 measure epoch, the drainage was checked, and 

 lakes and marshes were formed in the depres- 

 sions of the surface. In these basins a fine 

 sediment was deposited, — -the 'fire-clay,' — 

 like the clay now found under some of our 

 peat-beds. When overgrown with vegetation 

 the roots of plants penetrating this silt drew 

 out of it iron, potash, soda, etc., leaving it 

 nearly pure silicate of alumina, and speciallj' 

 refractory ; whence its uses and name. 



III. The marshes and lakes were ultimately 

 filled with peat, which rose to a general level 

 near the water-line, and was sometimes thirtj' 

 or fort}' feet deep in the deepest parts of the 

 basins. 



IV. In places, water-basins remained such 

 through a considerable portion of the time 

 occupied in the accumulation of the peat ; and 

 sluggish streams flowed through the marshes, 

 connecting these basins, and transporting to 

 them fine sand, clay, lime, iron, etc., which, 

 mingling with the completelj' macerated vege- 

 table tissue, formed cannel coal, black-band 

 iron-ore, and bituminous shale. After a time 

 these basins also wer-e filled with peat growing 

 from the margins, just as our lakelets are now 

 filled, and converted into p^at-marshes. 



V. After ages had passed with the phj-sical 

 conditions described, a subsidence caused a 

 submergence of the peat-marshes, which first 

 resulted in the destruction of the generation 

 of growing plants that covered them. These 

 dropped, in succession, leaves, twigs, and 

 branches; and, finally, most of the standing 

 trees fell. Some, however, continued longer 

 to maintain an upright position, while the fine 

 argillaceous sediment suspended in the water 

 was slowly deposited around them, to form the 

 roof shale, — of which the lower laj-ers are 

 charged with the d&hris of the plants growing 

 on the marsh ; the upper layers, deposited 



when these were all buried, nearly barren of 

 fossils. 



VI. The weight of the superincumbent mass 

 pressed down the bed of peat ; which, consoli- 

 dated by that process, and undergoing internal 

 chemical changes, ultimately became a bed of 

 coal, thickest in the deepest part of each basin, 

 thinning and rising on each side up to its edge, 

 which remains to mark the original level of 

 the surface of the peat-marsh. 



Thus, and in no other conceivable waj', was 

 the resulting coal-bed made six feet thick in 

 the bottom of the basin, and running out 

 to nothing on the sides, thirty or forty feet 

 higher. 



The whole anatomy of the coal-seam shows 

 that it was formed where it is found ; the 

 erect trees and plant-bearing shale above, 

 the root-penetrated fire-clay below, the small 

 amount of ash (only the inorganic matter of 

 the plants) , with many other features it pre- 

 sents, making the theorj' that it has been trans- 

 ported untenable. J. S. Newberry. 



THE YALE OBSERVATORY 

 HELIOMETER. 



For the benefit of the non-astronomical 

 reader whose heliometric ideas are vague, the 

 instrument ma}' be defined as a measuring-ma- 

 chine in which the images of two stars, or other 

 celestial objects to be measured, are super- 

 posed in the telescopic field by the following 

 method : a telescope object-glass is cut across 

 one of its diameters, and the two halves thus 

 formed can be moved in opposite directions 

 along the line of section by the observer 

 while looking through the ej-e-piece. If he 

 were examining the sun, for instance, with the 

 two halves of the object-glass together, then 

 he would have an ordinar}' telescopic view of 

 the sun ; but let him separate them, and he has 

 the efl'ect produced in the sextant when the 

 two sun's images are separated by moving the 

 arm. Now, if he brings the two images tan- 

 gent first on one side and then on the opposite 

 side bj' passing one over the other, the dis- 

 tance the object-glass halves are moved can 

 evidentl}' be expressed in arc, when the focal 

 length is known, and is a measure of the sun's 

 angular diameter. The advantages of such a 

 method of measurement are onlj' to be fully 

 appreciated from certain considerations in 

 physiological optics, from which it seems to be 

 established that the most accurate measure- 

 ments b}' direct vision are to be expected 

 when the measuring-scale and the object meas- 

 ured are precisely similar in appearance and 



