DISCOVERY OP TRIPOLI OR POLISHING POWDER. 



methodH of 

 Jor the mic- 



^> 



^t^ 



do 



back Bgain in the oppniiite direction, reproduc- 

 init, tirHt, the oriKinal rectangular maM with 

 »il itH Hlata piled one ahove the other, and then 

 the lonK chain of rodH exten<led the other way. 

 The Hint^iilarity o> these inotioni has iinpreHwed 

 Dr. ( 'nr|>enter ho strongly tliat he directH spfcial 

 attention t« them iu a footnote in hin work up- 

 on "The Microscope." (Op. cit. ch. vi , p242, 

 ed. 1H7.').) 



NAVICULAB. 



Another very pretty and very eauily rf- 

 cured spectacle ciin be nhtr' d by placing 

 under the inicroHcope a minute drop of muddy 

 water from aliiiont any of our fresh water 

 ponds or ditches and <>hservin»{ tlie little 

 Aaviculit sailiii); in twos and threes and some- 

 times in (luite nunierous fteets tlin>ugh the 

 bays and channels formed l>y the sand grains 

 and other debris that have Iteen put upon the 

 fllido alont; with them. Hometimes they seem 

 to be runnint; races. At other times thev man- 

 ceuvre about and run aboard of eai-h other in a 

 way that almost gives one the notiim of an old- 

 fashioned nnval buttle between wooden men- 

 of-war. Different obttervers hold difTerKrit 

 theories as to the way iri which these rutii>us 

 motions are effected, but the prevailing opinion 

 is that they are caused by the diutom'H im- 

 bibini{ some of the water in which it floats 

 throu.{h one set of its apertures and discharg- 

 ing it through another set. It munt be noticed 

 ihikt these apertures exist in the siliceous shield 

 only, and are closed at the bottom l)y the 

 external cell-membrane that encloses the 

 endochrome, hence if such an imbibition does 

 take ulace it must be by endosmose and have 

 something to do with the process by which the 

 plant obtains its nutrition. The great major- 

 ity of observers deny the existence of vibrattle 

 cilia or any other special organs of locomotion 

 among the Diatomuctut. Iu geological distri- 

 buticm the Diatoms are found ranging as far 

 backwards as the (^halk Formation, but their 

 iSrst, appearance was probably earlier than 

 this. At the present day their distribution in 

 place U -imply ubi({uitous. Uiventhe tiresence 

 of a little water an* ' some organic matter and 

 you will find live Dintoms almost anywhere. 

 Frenh, salt, and brackish water all have their 

 t>eculiar and characteristic forms, and there 

 are other forms which seem to inhabit evnry 

 kind of water. "There is hardly a roadside 

 ditch, water trough or cistern that will not 

 rewaril a search and furnish specimens of the 

 tribe" (Rev. VV. Smith). 



COLLECTION OK DIATOMS. 



A few bints on collections may not l>e out of 

 place here. In the course of a ramble in thi> 

 country your attention may be caught by a 

 thin, lustrous film, floating upon the surface of 

 some pond or ditch, and looking as if a little 

 oil or tar had been spilt there. If you skim 

 this (iff and examine it you will probably find 

 it ctmiposed largely if not altogether of Dia- 

 toms. Similar films may l)e seen sometimes 

 upon the surface of the nmd, where little pools 

 have been recently dried up, and these if care- 

 fully searched and examined will probably 

 yield a similar result. While walking near 

 the sea shore you may notice upon stones, sea 

 weeds or wooden surfaces that nave been sub- 

 merged by the tide, a red-ochrey looking 



incrustation something like a film of iron rust. 

 On scraping ofT and examining this you will 

 probably find a mixture of Diatoms and ex- 

 tremely line sand. The brown streaks that are 

 sometimes seeii ii> sea frotii are also 

 worth examination and will rarely 

 disap|)oint you. Again, in runn'ng streams 

 near the shore and in places where the 

 full force of the current is checked a little,you 

 may see long feathery clouds anil filaments at- 

 tached t<i the submerged stems of larger plants 

 BUvl wavering aUiut with the current. Strip 

 off and exatrune these and you will probably 

 get Diatoms again. After a little experience 

 in Diatom hunting you will acquire a certsin 

 sense of intuition that will tell you the 

 moment that you look at them which are th' 

 likely spots to search for what you want. Like 

 many other sports this one has a pleasing' ele- 

 ment of uncertainty connected with it. As 

 all Diatoms are pretty much alike to the 

 naked eye you never can tell what your gather- 

 ing consists of imtil you have taken it home 

 and examined it. It may contain many rare 

 and choice forms or it may l>e altogether made 

 up after the most familiar and least intere.nting 

 kinds, but in any case it is likely to contain a 

 numl)er of (iretty and interestint; things which 

 are not Diatoms at all. lience it follows that 

 you cannot practically study the Diatoms with- 

 out at the Hitmn time incidentally learidng li 

 Kood deal about a number of other minute 

 forms of orgunic life. Some c(. Hectors CHny 

 along with them a powerful pocket ndcroHcope 

 magnifj'ing up to 1(X) or 2(J() diameters and 

 "sample'' every gathering as they make it, rt- 

 je<;tiHg all that they don't want to keep, bnt 

 ttiis is more trouble th:in most amateurs will 

 care to tiikij and does not perhaps save ni'^ch 

 time after all. 



APPAHATtJS roR COLLECTING. 



The apparatus reipured for collection is very 

 simple, and 1 show you one here which I have 

 used a goml deal and can "confidently recom- 

 mend" as being effective while at the same 

 time it is neither costly,complicated norcumber- 

 some. You require then a water-tight tin box 

 of a convenient siee and shape to be carried in 

 your coat p >cket and to contain a bottoudess 

 tin cup about three inches in diameter and one 

 inch in depth and having a small side handle; 

 also a nuiidier of pieces of muslin or very 

 "o|)en-wnve" cotton, each big enough to cover 

 the bottoL'Q of the cup ancl allow a slight mar- 

 gin all around it. The lower edge of the cup 

 had better be "wired" so as to tiive a grip to 

 the elas ic band with which you secure 

 your muslin filter to it. When you want 

 to capture a fixating film you take your cup 

 and make a bottom for it of one of ymir musliu 

 rat<s secured in its place by an elastic band (of 

 which you had better bn provided with several, 

 as these are very apt to get lost), then <lip out 

 what you want and strain it. If y<:ur arm is not 

 long enough you can attiich your cup by means 

 of its handle to a walking stick, if this is still 

 too short you can in most rural localities easily 

 extemporise a longer handle from the nearest 

 convenient bush. Films attached to the rur- 

 face of stones, mud, posts, ko , may be scraped 

 off (taking care to remove as little extraneous 

 matter as possible along with them) and folded 



