f 62 9 ] 
times by one's felf, but it is very proper, and frequently 
neceffary that others fhould repeat them alfo, and 
fhould even fometimes hit upon the fame themfelves. 
And then it is, that by the means of thefe different ob- 
fervacions carefully compared with each other, we may 
come to be better affured of the various fads we are 
enquiring about. Befides which it may be noted, 
that the number of objefts, that fhould in this cafe 
be attended to, is really too great to be fufficiently 
obferved by any one Angle perfon. 
I believe it will not here be improper, to give 
the defeription of that apparatus I have made ufe of 
my felf, and by which I have been enabled to muke 
my experiments. This defeription will render what 
I have further to fay the more intelligible 5 and will 
perhaps contribute to make others more capable of 
judging, what degree of credit fhould be given to 
the feveral fatts, I may have occafion to relate. 
Thofe alfo who fhall be willing to obferve regularly 
themfelves, either the fmall water-infe&s mention'd 
in this paper, or any others they may happen them- 
felves to meet with, will not, I am perfuaded, be 
difpleafed with the defeription of an apparatus , 
which they will frequently find ferviceable to them 
in .their enquiries. 
The principal benefit I received from it myfelf 
was, that I was thereby enabled to obferve with 
the feveral magnifiers of my microfcope, fmall 
water Infeds, whilft in a glafs containing water fuf- 
ficient to let them live therein, much in the fame 
way as they would have done, had they ftill been 
in the ditches or other waters from whence they 
were firft taken. 
If 
