Monthly Mroses plea CORRESPONDENOE. 237 
Mn. Royston-Pigorr’s Views. 
To the Editor of the * Monthly Microscopical Journal.’ 
BALLINAMALLARD Rectory, Co. FerMANAGH, 
September 10, 1870. 
Sir,—Will you allow me space in your Journal for a few remarks 
on Dr. Pigott’s recent discoveries. Ido not refer to the question of 
the Podura-seale ; for as Mr. Wenham has undertaken it, others may 
be well content to leave it in his hands. The discoveries I allude to 
are those contained in his two last papers. As he has declared that 
his motto, optically speaking, is “Onward,” and repeatedly protested 
against the folly of our remaining satisfied with our present attain- 
ments instead of pressing onward to “higher things,” and as these 
papers are avowedly offered in illustration of the onward movement, 
he will not, I am sure, be offended if we examine the worth of what 
he has himself contributed to this end. 
The subject of these papers, he tells us, is a difficult one. The 
problem is “ worthy of a great deal of hard labour;” and the student 
who attempts to follow him must be prepared for “laborious work at 
the logarithmic tables,” with more about the “analytic calculations,” 
and so forth. There is so much of this kind that a reader of average 
mathematical nerve advances trembling, expecting every moment to 
find himself sinking in a quagmire of Definite Integrals, perhaps 
required to solve an equation or two in Mixed Differences. And what 
are the problems thus brought in with flourish of trumpet and beat of 
drum? They are these :—Knowing the refractive index of a medium 
to calculate the refraction of a ray.—Knowing the refractive index to 
calculate the angle of total reflexion—Knowing the angle of refrac- 
tion to calculate the “deviation.” —Knowing that the refractive index 
between two media in the quotient of their indices, to calculate the 
quotient. 
These are the problems Dr. Pigott has undertaken to solve and 
“ tabulate.’ One naturally asks, Is he aware that he has been antici- 
pated in this field; that these “problems” are solved, with examples, 
in the introductory chapters of any manual of optics? Two of them 
are merely arithmetic exercises in subtraction and division; the other 
two Dr. Pigott will find in, e.g. Haughton’s ‘Manual’ (the first which 
comes to hand), at pp. 19 and 29, with illustrative examples. The 
tabulation on which he lays so much stress is simply a collection of 
such examples, for angles regularly increasing ; any one of which a 
beginner could calculate for himself in a few seconds whenever he 
might happen to need it; and for failure in which an undergraduate 
would instantly be “plucked” in any university in the kingdom. Our 
surprise at this method of advancing the higher optics is not dimi- 
nished when we come upon the following startling announcement :— 
“Tn all these inquiries it will save a deal of time to remember that 
when a ray passes from a rarer into a denser medium it is bent towards 
the perpendicular or normal at the point of emergence.” * The prin- 
oo 1, WEI 
