The great advantage which this telegraph possesses in transmitting messages with the rapidity of lightning, annihilating time and space, would perhaps be much lessened in its usefulness, could it not avail itself of the application of a secret alphabet. We will now proceed to describe some of the various systems by which a message may pass between two correspondents, through the medium of the telegraph, and yet the contents of that message remain a profound secret to all others, not excepting the operators of the telegraphic stations, through whose hands it must pass.

For this purpose let the telegraphic characters representing particular letters be transposed and interchanged. Then the representative of a, in the permanent alphabet, may be represented by y, or c, or x, in the secret alphabet; and so of every other letter. As there are twenty-seven characters in the telegraphic alphabet, they can, by transposition, furnish six hundred and seventy-six different kinds of secret alphabets; nearly two for every day of the year. Two persons have agreed to use, in their telegraphic correspondence, the secret alphabet. From the six hundred and seventy-six combinations, they have selected one for each day in the year, and given each their particular date. In the course of their business, it becomes necessary on the first of July, for one to transmit important information to the other. He then refers to the telegraphic book, for the alphabet belonging to that date, and from it writes his communication, as follows: The firm of G. Barlow & Co. have failed. He runs his eye along the alphabetical column for t, and finds that for the first of July it is e, that h is j, e is n, and in the same manner, he proceeds with the remaining letters of his message, which, when completed, reads as follows: Ejn stwz ys & qhwkyf p iy jhan shtknr. As every person employing the telegraph has his name, occupation and place of business registered in the record book of the office, with his telegraphic number, we will suppose, that Mr. Hammond, Builder, 57 Anson-st. Philadelphia, sends the above communication to the office for Messrs. Talford & Co. Lumber Merchants, 41 Bradford-st. New York. In the record, the former name is numbered 14; and the latter 31. The private message is then directed thus, No. 14 to No. 31, and reads thus: Mr. Hammond, &c. sends the following communication to Messrs. Talford & Co. &c. “The firm of G. Barlow & Co. have failed.” This message, in substituted characters, is copied at the receiving station, and immediately delivered. The messenger returns with the following: Syw fjhe hzyxce. To which is prefixed No. 31 to No. 14. This is sent to Mr. Hammond, who, on translating it, discovers that it must be answered by figures. He then refers to the secret numerals, under the date of the first of July, and finds the private numerals required are 897, 312, adding to it a few letters, when it reads thus, No. 14 to No. 31, 879, 312 rykkm. If it should happen, that on the 6th of December, or 13th of May, it was necessary to send a private communication, the secret alphabets of those dates are used, and so for any date of the year.

July 1st.March 28th.December 6th.May 13th.
A change to HA change to AA change to QA change to X
B change to QB change to NB change to PB change to M
C change to IC change to OC change to NC change to G
D change to RD change to VD change to OD change to T
E change to NE change to PE change to VE change to L
F change to SF change to CF change to AF change to F
G change to &G change to QG change to CG change to &
H change to JH change to DH change to RH change to K
I change to TI change to RI change to DI change to S
J change to BJ change to EJ change to &J change to N
K change to UK change to SK change to EK change to Z
L change to KL change to FL change to ZL change to J
M change to ZM change to TM change to FM change to P
N change to CN change to GN change to XN change to E
O change to YO change to UO change to GO change to U
P change to LP change to HP change to WP change to I
Q change to DQ change to BQ change to HQ change to V
R change to WR change to IR change to BR change to B
S change to MS change to &S change to IS change to Y
T change to ET change to JT change to UT change to O
U change to XU change to ZU change to JU change to H
V change to AV change to KV change to YV change to Q
W change to FW change to YW change to KW change to D
X change to OX change to LX change to SX change to W
Y change to VY change to XY change to LY change to A
Z change to GZ change to MZ change to TZ change to R
& change to P& change to W& change to M& change to C
1 change to 51 change to 61 change to 01 change to 7
2 change to 72 change to 12 change to 92 change to 8
3 change to 13 change to 73 change to 43 change to 6
4 change to 84 change to 24 change to 54 change to 9
5 change to 25 change to 85 change to 35 change to 4
6 change to 96 change to 36 change to 86 change to 1
7 change to 37 change to 97 change to 67 change to 0
8 change to 08 change to 48 change to 28 change to 5
9 change to 49 change to 09 change to 79 change to 2
0 change to 60 change to 50 change to 10 change to 3

The transposed secret alphabet is not perfectly secure for private messages, when the message contains more than eight or ten words. It is, therefore, necessary to adopt some of the following modes of making it perfectly incomprehensible, and beyond the power of any person to decypher it. Any one or two, or more, of these modes may be selected and combined for this purpose. Let the following key or transposed alphabet, be used in illustrating the following rules:

A to RF to XK to UP to EU to KZ to M
B YG BL VQ PV G& I
C ZH TM DR LW N
D AI WN &S FX J
E SJ CO QT OY H

1st. Let the last letter of a word remain unchanged, viz. Rome, transposed, lqde.

2d. Let the first letter of a word remain unchanged, viz. Rome, transposed, rqds.

3d. Let the first and last letter remain unchanged, viz. Rome, transposed, rqde.

4th. Let the middle letter of a word of 5, 7, 9 or 11 letters remain unchanged, viz. First, transposed, xwrfo, and in words of 4, 6, 8, 10 or 12 letters, let the two middle letters remain unchanged, viz. Rome, transposed, loms.

5th. Let the first, middle, and last letters of a word remain unchanged, viz. first, transposed, fwrft.