264 Ml* D. Erskine's description of 



In the preceding remarks, it lias been our object simply to 

 discuss the pnncipal agencies that must have been in opera- 

 tion, in order to prepare the way fur a more complete eluci- 

 dation of the subject, by future developments. 



The importance of these discussions to geology is not to 

 be measured by the length of the catalogue of pseudomorphs. 

 The same process that has altered a few crystals to quartz, 

 has distributed silex to fossils without number, scattered 

 through rocks of all ages. The same causes that have origi- 

 nated the steatitic scapolites occasionally picked out of the 

 rocks, have given magnesia to whole rock formations, and 

 altered throughout their physical and chemical characters. 

 If it be true that the crystals of serpentine are pseudo- 

 morphous crystals, altered from chrysolite, it is true also, as 

 Breithaupt has suggested, that the beds of serpentine con- 

 taining them, are likewise altered, although often covering 

 square leagues in extent, and common in most primary 

 regions. The beds of steatite, the still more extensive tal- 

 cose formations, contain every where evidence of the same 

 agents. The deposits of the so-called Rensselaerite, in north- 

 ern New York, are other examples of the widely extended 

 influence of the pseudoniorphic agencies. — American Journal 

 of Science and Arts, vol. xlviii., No. 1, p. 81. 



A netv Self- Acting Method of Taking the Buckets from the Pit 

 Mouth, and Shutting off the Steam from the TFinding Engine. 

 By Mr Daniel Ekskine, F.R.S.S.A., (with a Plate). Com- 

 municated by the Royal Scottish Society of Arts.* 



The object of this improvement is, to prevent the ropes of 

 coal-pit engines from being over-wound, and to prevent the 

 many accidents that occur by the buckets being carried over 

 the pulleys. To effect this, the bucket is taken off the pit 

 mouth and placed upon a platform, and the steam is shut off 

 from the engine without the assistance of the engineer. The 

 full bucket is then let down an inclined plane, the weight of 



* Read, and model exhibited to tlie Society, on 14th April 1845. 



