90 



The NaturalisTo 



of high power, with wide angular aperture and special methods of 

 illumination, but, in ordinary physiological and botanical work, one 

 meets with little that cannot be done with an ordinary inch and a 

 quarter inch objectives. The really important point in an object glass 

 is that it give a clear definition. As a microscope is meant to be 

 looked through rather than to be looked at, a long stand is a disad- 

 vantage, as rendering it heavy and cumbrous to carry about. The 

 great point in a stand is that the microscope shall be ready for work 

 the instant it is taken out of the box ; if it takes a quarter of an hour 

 in screwing and unscrewing before you can get to work, you are not 

 likely often to use it. It is better not to buy more apparatus at first 

 than you know how to use, but to add afterwards what you find you 

 require. There is one piece of accessory apparatus, however, which 

 adds so greatly to the working power of a microscope, that I would 

 advise every one to have it, viz., a double nose-piece, by which one 

 can change the object glass without the trouble of unscrewing and 

 screwing. 



The most formidable dif&culty in the way of the investigation of 

 some of what I have called the " neglected orders " is the want of 

 accessible handbooks. The observer in isolated country places has no 

 opportunity to hunt up information scattered through the pages of 

 scientific journals, and the transactions of learned societies — British 

 and foreign. For instance, there is no British work on fresh-water 

 algae more recent than Hassall's, which was published at 36s. in 

 1845, and of which second-hand copies are now sold for £4 4s. 

 On the other hand it may be said that if more observers worked at 

 theso orders, to get together materials, and create a demand for 

 handbooks, the books would soon be written. 



It may be said, with much justice, that any one of the natural 

 sciences opens to ns such a wide field that we cannot expect to 

 cultivate the whole of it successfully, but must confine ourselves to 

 one corner if we wish to study it thoroughly. This, however, is no 

 reason why all the cultivators of the field should choose the same 

 corner. It is a question whether it is better that we should have a 

 wide or a deep knowledge — should know " multa ' or " multum^^ — - 

 should have a superficial knowledge of many subjects or a profound 

 knowledge of a single subject. I think that of the two, to have a 

 wide knowledge of many matters tends most to expand a man's mind 

 and sympathies, and to render him an intellectual and agreeable 

 companion ; but that by confining his attention to one thing, and 

 studying that deeply, a man of average mental power is more likely 



