HARDWICKE'S SCIENCE-GOSSIP. 



225 



marks are made of two species " more remarkable | 

 than others in the regularity of their processional ' 

 marchings." " These are found in the south of 

 Europe, but are not indigenous in Britain. The 

 one named by Reaumur the Processionary {Cnetho- 

 campa processioned) feeds upon the oak; a brood 

 dividing, when newly hatched, into one or more 

 parties of several hundred individuals, which after- 

 wards unite in constructing a common nest, nearly 

 two feet long and from four to six inches in 

 diameter. It is not divided into chambers, but 

 consists of one large hall, so that it is not necessary 

 that there should be more openings than one; and 

 accordingly, when an individual goes out and carpets 

 a path, the whole colony instinctively follow in the 

 same track, though, from the immense population 

 they are often compelled to march in parallel files 

 from two to six deep. The procession is always 

 headed by a single caterpillar ; sometimes the leader 

 is immediately followed by one or two in single file, 

 and sometimes by two abreast. A similar pro- 

 cedure is followed by a species of social caterpillar 

 which feeds on the pine in Savoy and Languedoc, 

 and their nests are not half the size of the preceding ; 

 they are more worthy of notice from the strong and 

 excellent quality of their silk, which Reaumur was 

 of opinion might be advantageously manufactured. 

 Their nests consist of more chambers than one, 

 but are furnished with, a main entrance, through 

 which the colonists conduct their foraging proces- 

 sions." 



The lady whose remarks are recorded above has 

 since written that the species she observed feeds 

 upon the pine-trees in the neighbourhood of 

 Mentone. S. W. U. 



THE MICROSCOPE AND MICROSCOPIC 

 WORK. 



No. X.— By E. Kitton. 



THE term Engiscope was used by Dr. Goring to 

 distinguish those instruments by which the 

 image of an object was exhibited magnified by an 

 eyepiece. The image might be produced either by 

 reflectors or refractors (compound microscopes). 

 He considered that those instruments with which we 

 look at the object itself should be called micro- 

 scopes, and as the magnifier might be a doublet or 

 triplet, it could not then be called a simple micro- 

 scope, but was in reality a compound one. The 

 name, however, never became popular, and the term 

 microscope is now generally understood to mean a 

 compound instrument. The term aplanatic (without 

 error) ought to be used instead of achromatic ; a 

 lens might be achromatic (that is, free from coloured 

 aberration) and yet be a very imperfect one, unless 

 its spherical aberration was also corrected. 



Having briefly described the microscopes of fifty 

 years ago, we will endeavour to give some idea of 

 the work they were capable of performing, and 

 perhaps we cannot do better than glance at the 

 work done by Messrs. Goring and Pritchard. We 

 will suppose, to quote Dr. Goring, that " the engi- 

 scope is set up and prepared for action ; and ob- 

 serve, gentle reader, that here you may set up your 

 staff, and proceed no farther unless you like . . . 

 Now, mind what I say, this instrument is like the 

 Irishman's crooked gun, which used to shoot round 

 a corner." (This of course alludes to the object 

 being at right angles to the line of vision.) The 

 Doctor then goes on in his quaint way to direct the 

 student how he is to place the object, bring it into 

 focus, &c, in all of which directions he is very 

 explicit. He concludes with the following advice : — 

 "Now, if you should not happen to succeed in 

 getting everything to go exactly to your mind at 

 first, do not curse the instrument by your gods, and 

 throw your wig behind the fire, and then dance up 

 and down the room like a maniac, as I once saw a 

 Erenchman do; but have a little patience, read my 

 directions over again, weigh well the import of every 

 sentence, and try your luck over again." 



The Doctor gives a humorous dialogue which is 

 supposed to take place between an old naturalist 

 who swears by the simple microscope. " If the 

 reader must know the names of the parties, they are 

 Tobias Oldbuck, Esq., the naturalist, and Mr. 

 William Putty, the optician. Lest I should be 

 accused of putting nonsense into the former gen- 

 tleman's mouth, I must state that he only expresses 

 opinions current among observers of this enlightened 

 age, and which I have frequently encountered in 

 society." 



" I must positively introduce my personages to 

 the reader. Mr. Oldbuck is an old bachelor of 

 about sixty (a descendant of Oldbucks of Monk- 

 barns). He always wears a very natty wig made 

 by an eminent artist ; his clothes are of the hue 

 scientific brown study colour ; he has not altered 

 the cut of them, or the model of his hat, or any of 

 his opinions on any subject, and declares he never 

 will, thinking it beneath his dignity either to learn 

 or unlearn anything at his time of life. Having 

 described his costume, that outward and visible 

 sign of a man's character, I do not think it neces- 

 sary to say anything more about him, except at one 

 period of his life he was far gone and most intently 

 engaged in constructing object glasses for micro- 

 scopes, which, however, he abandoned as an imprac- 

 ticable job. When another person afterwards 

 succeeded in producing them, Mr. Oldbuck's pride 

 was wounded in the tenderest place, for he con- 

 sidered himself a perfect giant in all sorts of micro- 

 scopic science : in consequence the sight of an 

 engiscope ever after turned his stomach. 



"Mr. William Putty is an enthusiastic young 



