Protnincnt Yorkshire Workers — Henry Clifton Sorby. 141 



followed, by the aid of which it was possible to calculate the 

 approximate temperature at which certain minerals had been 

 formed in Nature. 



From the foregoing notes it will be seen how deeply indebted 

 present-day g-eologfists are to Sorby's pioneer work in reg-ard to 

 the microscopic structure of rocks. In fact, a study of Dr. 

 Sorby's work is almost an epitome of the history of geological 

 science in recent years.* So long ago as 1872 the Dutch 

 Society of Science awarded him the first large gold Boerhaave 

 medal for hax'ing done more than anyone else to advance the 

 sciences of geology and mineralogy during the preceding 

 twenty years. 



From the study of the structure of rocks followed that of 

 meteorites, and in order to properly consider the latter an 

 investigation of artificial iron was started. This was in 1863, 

 and in the following 3^ear a paper was read to the British 

 Association on the subject, the full economical value of which 

 remained unrecognised for over twenty years. In 1887, however, 

 the Iron and Steel Institute appointed Dr. Percy, Sir Henry 

 Bessemer, and Dr. Sorby to decide upon the best method of 

 illustrating a complete paper on the subject. Since then the 

 importance of a microscopical investigation of iron and steel 

 has been generally recognised. ' In those early days,' writes Dr. 

 Sorby, ' if a railway accident had occurred, and I had suggested 

 that the company should take up a rail and have it examined 

 with the microscope, I should have been looked upon as a fit man 

 to send to an asylum. But that is what is now being done.' 

 What Dr. Sorby proved was that various kinds of iron and 

 steel consist of varying mixtures of well-defined substances, 

 and that their structure is in many respects similar to that of 

 igneous rocks. 



Following this much work was accomplished in connection 

 with blow-pipe chemistry, and he showed that much could be 

 learned by studying the microscopical character of the crystals 

 deposited in blow-pipe beads allowed to cool very slowly over a 

 lamp. 



Continual work with the microscope, particularly relating to 

 the study of meteorites, led to several improvements being 

 made in connection with the instruments. He invented the 

 spectrum microscope, with a new arrangement to get what is 



* In the 'list of authorities' in Geikie's 'Text-book of Geology" Dr. 

 Sorby is responsible for more references than is any other author. He is 

 also one of those included in Geikie's ' Founders of Geology.' 



igo6 May i. 



