DIRECTIONS FOR THE MICROSCOPE HISTORV. 323. 



Every Entomologist should keep an exact journal of the insects he 

 collects ; with an account, as far as possible, of the place, food, times of 

 appearance, &c. and place to each insect a ftumber corresponding with 

 that of his journal ; he should also make a catalogue in which the 

 names, generic and specific, are to be expressed, as also the synonyms, 

 with reference to such authors as have described them. In his jour- 

 nal he must also insert observations on their manners, ceconomy, &c. 

 to illustrate as far as possible their natural history, for there is little 

 doubt that many valuable discoveries are yet to be made by a proper 

 attention to insects. 



DIRECTIONS FOR THE MICROSCOPE. 



Microscope — an optical instrument, by means of which very mi- 

 nute objects are represented exceedingly large, and viewed very di- 

 stinctly, according to the laws of refraction or reflection. 



Microscopes are properly distinguished into simple or single, and 

 compound or double. 



Microscopes, s/wg/e, arc those which consist of a single lens or a 

 single spherule. 



Microscopes, compound, consist of two or more lenses duly com- 

 bined. As optics have been improved, other varieties have been con- 

 trived in the sorts of microscopes ; hence we have rejlecting micro- 

 scopes, water microscopes, &c. Each of these two kinds has its pecu- 

 liar advantage ; for a single glass shows the object nearer at hand and 

 rather more distinct; and a combination of glasses presents a larger 

 field, or, in other words, exhibits more of an object equally magnified 

 at one view. As each of these has its advantages, each of them has 

 its advocates, at least in practice. The celebrated Lceuwenhock never 

 used any but single microscopes; and, on the contrary. Dr. Hook made 

 all his observations with double ones. 



History — When, and by whom, microscopes were first invented is 

 not certainly known. Huygens tells us that one Drebell, a Dutch- 

 man, had the first microscope in the year 1621, and that he was re- 

 puted the first inventor of it ; though F. Fontana, a Neapolitan, in 

 1(3 16, claims the invention to himselt, but dates it from the year x^JlS. 

 As a telescope inverted is a microscope, the discovery might easily 

 enough have arisen from thence. 



Nothingmore is certain concerning microscopes, than that they were 

 first used in Germany about the year 1621. According to Borellus, 

 they were invented by Zacharias Jansen, in conjunction with his son, 

 who presented the first microscope they had constructed to Prince 

 Maurice^ and Albert archduke of Austria. William Bordl, wiio 



X 2 



