PREFACE. 



The publication of this little work lias been under- 

 taken with a view to encourage the practice of 

 Micro-photography, and afford a ready means of 

 obtaining information without the trouble of refer - 

 ing to the innumerable papers on the subject, scat- 

 tered up and down several scientific periodicals and 

 publications. 



As far as possible we have mentioned the sources 

 from which our informntion has been derived ; many 

 have no doubt been overlooked, but the absence of a 

 library for reference, and our isolated position, must 

 serve as an excuse. 



Our thanks are due to several friends, for their 

 kindness in supplying any information required, but 

 especially to the Rev. G. B. Powell who revised all 

 the proofs, and whose valuable services have contri- 

 buted in no small measure to hasten the comple- 

 tion and publication of the work. 



A. Cowley Malley. 



Hunslow, Shropshire. 



