PREFACE. XI 



oinit the separate determination of sand, and the extraction of the 

 soil with carbonic acid -water (both intended to be performed 

 hereafter). I have substituted for the determination of moisture 

 contained in the air-dried soil (varying greatly within brief periods), 

 that of the moisture absorbed by the same at a fixed temperature 

 if possible, in an atmospere at the point of saturation, with aque- 

 ous vapor ; which renders the determinations directly comparable, 

 and seems to offer a very important element in the determination 

 of the treatment of soils. Not having had a space of a perfectly 

 uniform temperature at my command, the temperatures at which 

 the saturation took place, have varied somewhat, as will be seen 

 by reference to the analyses ; but it is my intention to determine, 

 at the earliest possible moment, the law of variation in this respect, 

 so as to render the results strictly comparable. I hope that the 

 imperfections of the work in a scientific as well as in many other 

 points of view, may meet with lenient judgment at the hands of 

 those at least, who have experienced the difficulties besetting an 

 observer who has to rely almost entirely upon his single-handed 

 labor, in the numerous departments of science involved in a work of 

 this kind. 



It may be noticed by those possessing the Report of my imme- 

 diate predecessor (L. Harper), that many facts and 'localities 

 mentioned there, are referred to and described in the present one 

 also. As stated at first, it has been my aim to communicate as 

 completely as possible, all reliable observations and results here- 

 tofore obtained in connection with the Survey ; and wherever I 

 have availed myself of the observations, either of my predecessors, 

 or of other scientific observers, I have given due credit. With 

 reference to Harper's Report, therefore, I have simply to say, that 

 nine-tenths of all the data given there in relation to the north- 

 western portion of the State, are extracts, sometimes literal, from 

 my field notes, made in the capacity of Assistant in 1856 ; the 

 observations then made being here presented in the light in which 

 they appear to me, and with the conclusions to which, in my 

 judgment, they legitimately lead. Owing to the want of his field 

 notes, as well as those of his predecessors, I have been compelled 

 to rely chiefly upon my own recollection with reference to the 

 observations jointly made in the southern portion of the State, in 

 1855, so far as I have not since re-examined the region personally. 



