306 Rev. E. Craig on the Measurement of the 



cipally of calcareous matter, the matrix being of that nature, 

 although siliceous matter may also possibly enter, to a greater 

 or less extent, into their composition. It would be a matter of 

 interest if the friends of science in France would have this mat- 

 ter ascertained. 



The other instance mentioned by Cuvier,* refers to fossil 

 scales supposed to belong to crocodiles found in the neighbour- 

 hood of Argenton, in the Paris basin. They have a consider- 

 able resemblance to those of Caen ; and it is remarkable that 

 they are described as having a very prominent bony crest, 

 " une Crete osseuse tres saillante,'" — a character apparently 

 having some connection with the circumstances formerly stated 

 as to carinated scales. These fossil scales would also be well 

 deserving of an examination. 



I could have wished to have made my examination of such 

 relics more extensive, but in this place no other materials were 

 to be met with. 



Edinbuiigh, M July 1835. 



Notice of' an arrangement for the measurement of the Angles of 

 very Minute Crystals. By the Rev. Edwakd Craig, A.M., 

 Oxon., F. R. S. E, Councillor of the Society of Arts.j- 



In the winter of 1833 I was led to Investigate the phenome- 

 na of chemical action under the microscope, and subniitted to 

 the consideration of the Royal Society of Edinburgh, during 

 that session, a short paper on the subject. The method which 

 I adopted was, to place very minute portions of chemical agents 

 upon thin plates of flat glass, and to bring them together; then, 

 when one plate was pressed down upon the other with a uni- 

 form, or nearly uniform, pressure, the substances under exami- 

 nation were reduced to a very thin film, capable of very distinct 

 observation, by transmitted light, and of being easily brought 

 under the focus of a highly magnifying lens. 



In this way an endless variety of operations were observed, 

 especially those connected with the application of galvanism to 



• Os3. Fos. torn. V. part 2. p. 168. 



+ Received 8th April, and read and exhibited to the Societj of Arts for 

 Scotland 20th May 1835. 



