74 
THE YOUNG SCIENTIST. 
observers. It is quite probable that Herschel 
was correct in his surmise, as there is abundant 
proof of activity quite near tliis spot. 70 is very 
briofhtat Full Moon, and the surrounding bright 
streaks may be seen extending out into Mare 
Serenitatis (H), a nearly circular plain, 430 miles 
in diameter. Near its west edge is a low ser- 
pentine ridge, which may be best seen five or 
six days alter New. Upon the south boundary 
of H is the grand mass of mountain peaks called 
Caucasus (75). The peaks tower as lofty as any 
on the Moon, reaching as high as 19,000 feet. 
Their narrow shadows are drawn out into line 
points, forming a grand spectacle in the First 
Quarter. 
Eudoxus (77) and Aristoteles (78) are a noble 
pair of craters, not easily seen at full, as the 
region is then dotted with thousands of bright 
specks. The terraced wall of 77 rises 11,300 feet 
above the west interior, and is crowned on that 
side by two turrets 15,000 feet high. 78 is more 
than 50 miles broad, and nearly as deep as 77, 
but with a much richer wall, being very remark- 
able for the rows of minute hillocks, which 
nearly surround it in lines, pointing to the 
centre of the crater ; the linest specimen of this 
not uncommon arrangement. This same ar- 
rangement may be seen around 77 also, in the 
Eirst Quarter. On the S. and S.W. of 77, down 
to Mare Serenitatis and the Caucasus, the sur- 
face is crowded with innumerable hillocks, like 
stars in the most crowded part of the Galaxy. 
Penn Yan,N. Y. 
Filing Flat and Other Surfaces. 
This is one of the branches in which, as a rule, 
most amateurs fail, and failure is not confined 
to them, as it is one of the most difficult opera- 
tions which the professional engineer has to 
perform. I think, therefore, a short practical 
article will be acceptable tomany of our readers, 
and it will be my endeavor to make my re- 
marks as concise as possible, and to convey as 
much information as space will admit of. First, 
then, as to the selection of files. This must, of 
course, depend entirely upon the nature of the 
material about to be Avorked. As to the various 
shapes and forms that are to be filed, these we 
will leave alone, pro tern, and be contented with 
trying to file a flat and true surface. This accom- 
plished, whoever the person may be, he is entitled 
to consider himself a good vice-man, it being 
well known that this is one of the greatest dif- 
ficulties connected with tliis particular art. 
Having selected a piece of brass to begin upon, 
about 2h inches square, take a 10 inch bastard 
file One reason why I suggest brass to begin 
upon is that when the file is worn too much for 
.brass it will be in good condition for steel or 
iron. Economy with files must form one part 
of tlie workman's education in filing. Some 
men will wear out twice the quantity of files 
that another will, and it is only because the 
one is careful and the other is utterly regard- 
less of the files, simply because he does not have 
to pay for them. Before beginning operations, 
another important matter to attend to, is the 
fixing of the vice, and this should be so ar- 
ranged that when the work is held in it, the 
surface to Vje filed will come to an elevation just 
below the elbow. Like many other things, there 
is a slight diversity of opinion as to the exact 
height it should be held. Some advocate the 
work being level with the elbow. I think it will 
be better for the workman to so adjust his work 
as to suit his own comfort, regardless of its be- 
ing an inch above or below any given point. It 
may appear to some a matter of little or no 
consequence how a man stands in position when 
at the vice, but this is to me one of the best tell- 
tales of a good workman. Nothing is more ob- 
jectionable to an experienced man than to see a 
fitter with, it may be, his left foot two feet or 
more from his vice, or, on the other hand, lean- 
ing against the bench and using two inches only 
out of a ten inch file. To be an efficient vice- 
man position must not be overlooked. The left 
foot should be about six inches from the bench, 
and the heel of the right between 30 in. to 36 in. ; 
the left knee slightly bent forward, the elbows 
kept well into the side, and in taking the for- 
ward stroke, the weight of the body should go 
with the bend of the knee. As to the distance 
given for the feet, a deviation may be necessary 
in many cases in consequence of difl'erencc in 
the height of various men. But a few strokes 
of the file will soon show if the position is suit- 
able. The file must be firm ly held in the right 
hand, and the left hand should bear upon the 
front end of it, as the file must only be allowed 
to cut one way, that is, forward. The pressure 
must be relieved when it is drawn back; if not, 
much damage will be done to the file, in the 
way of breaking off the teeth. I have many 
times had men come to me M'ith a file, and as- 
sert that it was of no use, being too hard, caus- 
ing the teeth to break. Even so-called practiced 
hands have done thi^, but the cause of this has 
been not knowing now to use the tool. Nothing 
but long practice will enable any one to arrive 
at any state of perfection. In holding the file 
firmly in the right hand, it must not be clinched 
so that the wrist becomes cramped, but suf- 
ficiently rigid not to allow the file to turn all 
ways. The action must be a natural one, and the 
movements backwards and forwards be in a 
horizontal direction. After several trials, it may 
be found the same result has been obtained, that 
