NATURAL HISTORY OF THE DIATOMACE^. 481 



tained in them, or in the strata above or below them, should be gathered, 

 and their position noted on the labels accompanying them. All specimens 

 should be kept carefully separate (not even permitting them to come in 

 contact) by wrapping each one in paper, placing within a label having 

 written upon it in ink the exact locality, date of collection, and name of 

 collector. It is also desirable that note should be made of the depth 

 from the surface at which the specimen was taken, together with any 

 other information that may be deemed of interest, as supposed extent of 

 stratum, slope-upwards towards north, south, east, or west, and thickness. 



Lacustrine Sedimentary Deposits. These were called by me at one 

 time sub-peat deposits, from the fact that all I had seen up to that time 

 had been discovered beneath peat; but as the number of these strata 

 which have come into my hands has increased, I have seen many which 

 do not occur under such circumstances; hence the above name has 

 been applied to them as being more appropriate, and indicating their 

 most common mode of occurrence. In England they are called fossil; 

 but in the true acceptation of that term the forms contained in them 

 are not fossils, but are identical with living species. 



They are generally of a pulverulent character, and, when dry, are of 

 little weight, so much so as to attract attention. When free from organic 

 matter, as occasionally occurs, they are quite white, looking almost like 

 powdered starch ; but most commonly they are grey, which looks dark 

 while the material is wet, but when dried the color is light. A mass of 

 about six or eight pounds' weight should be secured, and the same pre- 

 cautions as to keeping separate and labelling specimens adhered to, as 

 have been already mentioned. As these beds are seldom of any great 

 extent (they often soon become obliterated or covered up), it will be well 

 to secure a good supply of the material while it is accessible. If any 

 shell, wood, or other organic remains should be found dispersed through 

 the deposit, or overlying or beneath it, they should also be secured, and 

 their position recorded on the label. Likewise, a sample of any superin- 

 cumbent peat should be kept for future examination. In Sweden and 

 Norway, and in Lapland, these deposits have been used to eke out a 

 scanty supply of flour during bad seasons ; but they can hardly be said 

 to be food, for they are not nutritious, but most likely only act by their 

 mass distending the stomach, and thus allaying for a time the pangs of 

 VOL. r. 63 



