iX Trcatfcif BODIES. Chap.rr 



But if che descending atomes, be in part carried along down 

 die lueain by the current of wind or water; yet fiill the current 

 bvrrrgeth with it new atomes into the place of thofe that are car- 

 ried away;and thcle atomes } in every point of place wherefocver 

 they are, do of thcmiclves tend per ptndicularly downwards ; 

 iTowbcTtihty are forced from the complete cftet of their ten- 

 cbmce,by the violence of the current :fo that in this cafe they are 

 moved by a declining morion, compounded of their own natu- 

 ndlrnocion v and of the forced motion 1 , wich which the (iream. 

 caniierB them. Now then if a. dcnfe body do fall into fuch a cur- 

 rent, where thefe difTerent nrotionsgrve their (ererall. impulfes, ic 

 will be carried (in fach fort as we fay of the ato*c$;lj>ut in ano- 

 ther proportion); mat ire a pcrpcndiailar bvit in amixt deciifluig 

 line : compoi:n Jed of tPre feveral innpuKcsvW 011 the atomcs and the 

 cacrcntcta give ir (in whicli alfo icis to be tetneir.br ed, hovrthe 

 current givedr aji impnlfc downwards, as well as floping ; and 

 pernd venture the- fhrongeft down-waida :} and the dcchn-ation 

 \till be marc or kflfe , according aj> the violent imf*ulfe prfiva-il- 

 eth more or liefle againft the nnturall motion. 



Batcdiisis not all thacis to be confickred in eflkiaaiirigthe de- 

 cHnatioiiofa ciemic- bodies motiorLwiiciai$rii>k3ng.in acurrenc 

 of wirwi OT water ;you; mtuft remember; chat the deiife body k fclf 

 harhia pattictdar virtue of its own^naimely it*derWity)by which 

 it received* and proieeuteth more firiJy its detErminatien dowa- 

 wards; and therefore the force ofrhat body in cutting its. way 

 t-hjoxigb rhe medium, i; aJfo to be confider.cd in this- catenas well 

 as abo^c, in calculating irs deciria ing from the perpendicular;. & 

 out of adl thcfe caafes w ii refulr a middle declination compound- 

 ell of trie rwotwi* of the water or wind both wayes, and of its 

 own morion by the perpendicular line. And finee of thcfe thiee 

 cauics of a dcnie bodies motiori,its own virtue in profecwting by 

 its dtnfity the dccctminarion ir requireth, is the moil effi- 

 cacious by much after it hath once received a determina- 

 tion from without; its declination will be but little if it 

 fate very denle and hcavie-. Bur rf it recede truck from dcn- 

 fnte > fb as to hare fome near proportion to the den- 

 fttie of the medium, the declination will be great. And in 

 a word, accord ing as the body is heavier or lighter, thedfcli- 

 nacion. will, be mo-ie.or JeiTeviai the firmc cutreot through not 



exaifily/ 



