LETTER OP SUBMITTAL. 



SIR : I have the honor to submit herewith for your inspection and ap- 

 proval Bulletin No. 13, devoted chieily to a discussion of the best meth- 

 ods of detecting the adulteration of foods. 



The first part, which is now placed in your hands, treats of dairy 

 products. Much interest has lately been manifested among those en- 

 gaged in agriculture in respect of the adulteration of butter, and this 

 l>art of the subject has been treated with greater detail than any other. 



It lias been my object in this work to determine the best methods of 

 analysis of the various products in question, and all the recent improve- 

 ments in analytical methods have been thoroughly tried, and those 

 which have given good results have been adopted in the analytical 

 work which has been done. 



Within the last year my division has been supplied with apparatus 

 for photo-micrography, and the illustrations in the following pages are 

 entirely the work of the division unless otherwise stated. 



Great benefit has been derived from this method of fixing photo- 

 graphic appearances, as the illustration of the crystalline characters of 

 butters and butter substitutes sufficiently show. The examination of 

 condiments, &c., the report of which will soon follow, was made al- 

 most entirely with the microscope, and the illustrations will show how 

 satisfactory this kind of work proves to bo. In the matter of photo- 

 graphic illustration no attempt has been made to conn' no the exhibition 

 to phenomenally fine specimens, but the ordinary appearance of the 

 field of vision has been reproduced. This, I think, is of greater advan- 

 tage to the general investigation than would be the publication only of 

 the strikingly good negatives. It is believed that by following the 

 methods of analysis recommended in the report it will be possible to 

 detect without fail any Adulteration of butter that could possibly prove 

 a commercial success. All other forms of ad ulteration will be sup- 

 pressed by the laws of trade. In addition to the report herewith sub- 

 mitted the following parts of the bulletin are almost ready for the press, 

 viz, condiments, sugar, sirup and honey, drinks and canned goods? 

 Hour and meal, tea and coflfee, and baking powders. Other parts will 

 follow as soon as time is afforded to submit all the process involved to 

 a thorough examination in the laboratory. 

 Respectfully, 



H. W. WILEY, 



Chemist. 



Hon. NORMAN J. COLMAN, 



(Commissioner of Agriculture. 3 



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