of Middle Latitude Sailing. 1 83 



page 175 of the second edition^of his excellent treatise ou Navi- 

 gation, published in 1831. 



These remarks are given, not in the spirit of acrimonious cri- 

 ticism, but purely to shew the inutility of making unnecessary 

 corrections in our best works, usually in the hands of ordinary 

 practical seamen. 

 54. South Bridge. 



Observations on the Structure of the Braiuy Sfc, 



The " Annalen der Physik und Chemie" vonPoggendorfF, No. 

 7, 1833, contains an essay by Professor Ehrenberg of Berlin, 

 entitled, " The necessity of a minute mechanical examination of 

 the brain and nerves in preference to the chemical analysis illus- 

 trated by observations,'^ in which there is given an account of some 

 observations recently made by him with regard to the minute 

 structure of nervous tissue, as seen by the aid of a very power- 

 ful microscope. 



Many attempts of a similar nature to examine the structure 

 of that fibrous-like texture which is in general seen in some 

 parts of a fresh brain, and which becomes more obvious when 

 tlie brain has been artificially hardened by steeping in alcohol or 

 a solution of the muriate of mercury, or by boiling in oil, have 

 been made ever since the microscope came into use, but these 

 attempts have led as yet to very unsatisfactory results. 



A hasty repetition of Professor Ehrenberg's observations has 

 not shewn us the appearances described by him, but the well 

 merited character for accuracy and skilfulness in the use of the 

 microscope which that observer has acquired by his interesting 

 researches on the structure and functions of Infusoria, makes us 

 hope that they may be found to be correct, and satisfies us that 

 a short account of them will at all events be interesting to ana- 

 tomists and physiologists. 



The discordance in the accounts given of the structure of the 

 brain and nerves by Leewenhock, Delia Torre, Monro, Barba, 

 Home, and others, and the unsuccess which has generally attend- 

 ed this investigation, may in some degree have proceeded from 

 unskilful management of the microscope on the part of some,— 

 from different modea^of examination having been adopted by 



