4 Marvels of Pond-Life. 



dred diameters/' or one hundred linear ; and the figures 

 100 would be appended to any drawing which might be 

 made from it. It is, however, obvious that the length 

 is magnified as well as the breadth ; and hence the 

 magnification of the whole surface, in the instance 

 specified, would be one hundred times one hundred, or 

 ten thousand : and this is the way in which magnifi- 

 cation is popularly stated. A few moments' considera- 

 tion will show that the scientific method is that which 

 most readily aff*ords information. Any one can in- 

 stantly comprehend the fact of an object being made 

 to look ten times its real length ; but if told that it is 

 magnified a hundred times, he does not know what this 

 really means, until he has gone through the process of 

 finding the square root of a hundred, and learnt that a 

 hundredfold magnification means a tenfold magnification 

 of each superficial dimension. If told, for example, 

 that a hair is magnified six hundred diameters, the 

 knowledge is at once conveyed that it looks six hundred 

 times as broad as it is ; but a statement that the 

 same hair is magnified three hundred and sixty 

 thousand times, only excites a gasping sensation 

 of wonder, until it is ascertained by calculation that 

 the big figures only mean what the little figures express. 

 In these pages the scientific plan will always be fol- 

 lowed. 



If expense is not an object, a binocular instrument 

 should be purchased, and it is well to be provided with 

 an object-glass as low as three or even four inches focus, 

 which will allow the whole of objects having the diameter 

 of half an inch or more to be seen at once. Such a low 



