SCIENTIFIC SUKVEY. 39J 



organisms. Another singular ftict affording additional evidence of 

 the utility of such bodies is their invariable presence in great num- 

 bers in all the imported guanos. Indeed so true is this, that the 

 poorer qualities of guano have been shown to be the very ones in 

 which the least number of the microscopic algae can be found. 



I therefore conclude that there can be but little doubt of the real 

 efficacy of such deposits, no matter whether fresh-water or marine, 

 and that the beneficial action which they exert upon the soil is to 

 supply a large amount of silica in precisely that condition from 

 which it may most readily be taken up by growing plants. As 

 many of these organisms are said to contain a trace of iron in their 

 composition, probably this element may also exert a beneficial 

 efiect. 



Of the total amount of such deposits in the State of Maine, little 

 is known. Even where their presence has been shown, the extent 

 and thickness of the outcropping beds has been seldom measured. 

 There can be little doubt, however, that a closer examination would 

 prove the quantity to be considerable. The localities now known 

 where diatoms exist in a fossil condition in this State are the fol- 

 lowing: — Bluehill Pond (discovered by Dr. C. T. Jackson); Brown- 

 field ; Newfield ; Round Lake, Calais ; Chalk Pond, Beddington ; 

 Adley Pond, PhiHips ; Bangor ; Chalk Pond, Waterford. 



The first of these deposits, that from Bluehill, has long been 

 known and the species contained in it already described. As the 

 four next deposits are but recently known, I will say a few words 

 as to their characters and the species they contain. 



Of the four specimens sent me for examination, that from the 

 Chalk pond, Beddington, is by far the purest and the richest. It 

 is as white as chalk, (for which it has probably been mistaken, 

 judging from the name of the locality,) is almost free from foreign 

 matter, and as you have informed me, covers some twenty acres, 

 being of unknown depth, but certainly several feet. The species 

 contained in it are the following: 



Eunotia triodon and diodon. Gomphonema capitatum. 



Eunotia pentodon. Coeconema lanceolatum. 



Eunotia serva. Orthosira aurichalcea. 

 Eunotia falx. = E. hemicyclus. Ehr. Melosira distans. 



Navicula firma. Himantidium arcus. 



Navicula ovalis. Himantidium bidens. 



Navicula viridis. Himantidium undulatum. 



Navicula serians. Himantidium gracile. 



