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RECOMMENDATIONS

OF THE ENDLESS SELF-COMPUTING SCALE.

Rochester, Jan. 19, 1842. The “Self-Computing Scale," by A. Palmer, is a very iri. genious and interesting instrument for performing most of the operations in arithmetic. The principle is very plain ; and the accuracy, and certainty, and rapidity of the results are very striking

C. DEWEY, Principal of Coliegiate Institute.

Rochester, January 19, 1842. Having particularly examined Mr. Palmer's "Self-Computing Scale," I fully concur in the above testimonials of Dr. Dewey.

SAMUEL LUCKEY, D. D.

Attica, March 5, 1842. From an examination of the “Self-Computing Scale," by Mr. Palmer, I can most cheerfully concur in the above recommendations, and hope it may be introduced into our schools and academies.

E. B. WALSWORTH, Principal of Attica Academy.

Buffalo, April 5, 1842. We have examined tne above mentioned Scale, and concur in the certificate of Professor Dewey.

W. K. SCOTT, Civ. Eng.
R. W. HASKINS, M. A.

tax.

Brockport, Feb. 19, 1842 I have carefully examined “The Endless Self-Computing Scale," by Mr. Aaron Palmer; and, without hesitation, give it as my opinion, that it will be found a very useful invention. All the problems in arithmetic can be readily solved upon it, and most of them with great expedition, particularly the rules for computing interest for months and days, at any per cent., the Rule of Three, and Fractions. In the apportionment of County, Town, and School Taxes, it will be found almost in. valuable, as it requires to be set but once, to show each man's

JULIUS BATES, M. A. Principal of Collegiate Institute.

Cambridge, Oct. 20, 1843. I have examined Mr. Aaron Palmer's "Endless Self-Com. puting Scale;" it is simple and most ingenious, and I cheerfully concur in Mr. Julius Bates's judicious recommendations of its utility.

BENJAMIN PEIRCE, Perkins Professor of Astronomy and Mathematics

in Harvard University.

Boston, October 24, 1843. Mr. Palmer's "Self-Computing Scale” is certainly a very ingenious arrangement of numbers, and it will save a great amount of time in the hands of those who have computing to perform, whatever be the subject of the computation.

FREDERICK EMERSON,

Author of the North American Arithmetic. I heartily concur in the above recommendation.

WILLIAM B. FOWLE, Toate Teacher of the Female Monitorial School, Boston

Boston, October 23, 1843. Mr. Aaron Palmer,

Sir: Your “Self-Computing Scale” appears to me an' exceedingly useful invention. I shall be glad to possess one of them, as it will save me much labor, and I doubt not that many persons will find the same advantage in its use.

Respectfully your servant,

JOHN S. TYLER, Votary Public and Insurance Broker

Boston, October 24, 1843. I have examined Mr. Aaron Palmer's “Self-Computing Scale;" it strikes me as being a very convenient labor-saving machine, and that it will be highly useful in calculating interest, general average, or dividends on a bankrupt's estate, and for other similar purposes.

S. E. SEWALL,

Counsellor at Law

I have examined " The Endless Self-Computing Scale” of Mr. Palmer, and with pleasure express my high admiration of it. It is constructed on the only principle acknowledged by scientific men, since the invention of Logarithms, adequale to such purposes. Over all sliding Logarithmic Scales, it possesses a vast superiority, both in facility of use and accuracy of result. For this superiority, it is indebted to its circular form. With a diameter of about eight inches, it is equivalent to a common sliding scale of four feet with its slide of the same length, making when drawn out, a rod of about eight feet in length. It will be seen that its accuracy will be proportionably greater, as a circle can be constructed more exact than such a scale.

G. C. WHITLOCK, Professor of Mathematics and Natural Science

in Genessee Wesleyan Șeminary. Mr. Aaron Palmer,

Sir: I have taken much pleasure in testing the power of your "Self-Computing Scale,” by examples from nearly all the arithmetical rules. I am particularly struck with its great facility and accuracy in computing interest, apportioning divi. dends, and performing proportions generally. From the best examination I have been able to give it, I think it at once a most simple and wonderful invention; and I am confident, that when perfected, it will come rapidly into extensive public use, and will prove of singular benefit to those having occa. sion to make frequent computations in Bankruptcy, Insol. vency, Insurance, Averages, Taxation, and the like hranches of business.

AMOS B. MERRILL,

10 Court Street, Boston.

THE TIME TELEGRAPH.

The Time Telegraph is composed of a beautiful steel plate engraving, neatly executed by G. G. Smith, of Boston, upon the surface of which is arranged in circles four lines or rows of numbers; upon the moveable circle is placed the names of the twelve calendar months, to which is affixed the number of days in each month, 365 making the entire circle; the inner row of numbers found upon the stationary circle, running from 1 to 365, is used for calculating time to come; the outer row of numbers on the stationary circle is reversed, and is used for the purpose of calculating time past. The manner of ascertaining the number of days from any given day in any month, is readily found by simply turning the moveable circle unto the day of the month from which you compute is directly opposite the gauge point affixed at the figures 365, then opposite the day of the month to which

you

wish to reckon is found the exact number of days required. Upon the stationary circle is also found the weeks, from one to 52; to these are added divisions of 30 days, so that any portion of the year can be brought into months as readily as the fingers of the hand can be reckoned. The Time Telegraph will be found of invaluable benefit in working equation of payments, &c.

Entered according to Act of Congress, A.D. 1845,

By Jown E. FULLER.

INTRODUCTION.

The undersigned, proprietor of the Copy Right of Palmer's Endless Self-Computing Scale, and hav. ing been engaged in introducing and selling the same for about' eighteen months past, and become exten. sively acquainted with the wants of the community, has been induced to introduce an improvement for which he has secured a Copyright, both for the Scale anc Key, and is assured that all persons in commencing the use of the Scale will be very much assisted. The character of the Scale is too well estab. lished to need remarks. Having personally introduced it to about Four Thousand persons; by very many of. yhom he has had repeated assurances of their high appreciation of its value, he can with confidence referothers who may wish to possess it, to any of those who may have used it in any of the various rules of Arithmetic. His only desire is that its future patronage shall be pro. portionate to its true merits.

JOHN E. FULLER.

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