USD $150
12″ / 10″ Power Log Exponential Log Log Duplex Slide Rule
White (Traditional) (T) coated aluminum construction, black and red scales, dual log scale design in one of Pickett’s most powerful rules. This is a very sophisticated 32 scale rule, made in the trademark aluminum body format by Pickett, with a less cluttered layout than the N4, but extremely powerful.
This rule and case are in good condition with some marking and wear on the case, including the name of a previous owner marked on the interior flap of the case. Includes original belt loop.
(32 scales)
Front – 2 sq. root scales, K, A, [ B, ST, S, T1, T2, CI, C, ] D, DI, 3 cube root scales
Back – LL0+, LL0-, LL1+, LL1-, DF [ CF, CIF, Ln, L, CI, C, ] D, LL2+, LL2-, LL3+, LL3-
Stock: 1
USD $165
12″ / 10″ Power Log Exponential Log Log Duplex Slide Rule
White (Traditional) (T) coated aluminum construction, black and red scales, dual log scale design in one of Pickett’s most powerful rules. This is a very sophisticated 32 scale rule, made in the trademark aluminum body format by Pickett, with a less cluttered layout than the N4, but extremely powerful.
These rules are in very good condition, with wear to the oxblood finish cases (with belt loop).
(32 scales)
Front – 2 sq. root scales, K, A, [ B, ST, S, T1, T2, CI, C, ] D, DI, 3 cube root scales
Back – LL0+, LL0-, LL1+, LL1-, DF [ CF, CIF, Ln, L, CI, C, ] D, LL2+, LL2-, LL3+, LL3-
Stock: 2
USD $185
12″ / 10″ Power Log Exponential Log Log Duplex Slide Rule
White (Traditional) (T) coated aluminum construction, black and red scales, dual log scale design in one of Pickett’s most powerful rules. This is a very sophisticated 32 scale rule, made in the trademark aluminum body format by Pickett, with a less cluttered layout than the N4, but extremely powerful. This set has the black finish case with pen holders and name window, as well as a belt loop.
(32 scales)
Front – 2 sq. root scales, K, A, [ B, ST, S, T1, T2, CI, C, ] D, DI, 3 cube root scales
Back – LL0+, LL0-, LL1+, LL1-, DF [ CF, CIF, Ln, L, CI, C, ] D, LL2+, LL2-, LL3+, LL3-
Stock: 1
USD $135
12″ / 10″ Log Log Exponential Duplex Slide Rule
EARLY ROUNDED CORNER MODEL. Yellow (ES) coated aluminum construction, black scales. This is a very sophisticated rule, made in the trademark aluminum body format by Pickett, and comes with the original leather case with belt loop.
(22 Scales)
Front – LL2+0.1, LL2-0.1, DF [ CF, CIF, L, CI, C ] D, LL3+1.0, LL3-1.0
Back – LL1+0.01, LL1-0.01, A, [ B, ST, T, S, C ] D, DI, K
Stock: 1
USD $65
Pickett 106C Proportional Scale 6″ Circular Slide Rule
Stock: 1
USD $59
4 Inch Simplex Circular
Pickett’s popular plastic commercial circular slide rule, with mark-up and discount functions. Very nice rule, with operating instructions on the face, used excellent condition. Convenient pocket size, very hard to find!
(4 Scales + directions)
Front – Profit mark up , Unit Cost, Profit Margin %, Discount %
Back – Blank
Stock: 3
USD $45
This is a very thorough and intuitive conversion set created by Pickett which uses interchangeable discs secured by a thumb screw to modify the rule for different unit conversions. The rule also features C & D scales for multiplication and division.
The original packaging is included, which features detailed and easy to understand operating instructions.
Stock: 1
USD $89
8 Inch Simplex Circular
Pickett’s popular full-sized plastic commercial circular slide rule, with mark-up, margin and discount functions. Very nice rule, with operating instructions right on the face, very good condition. This has a few surface scuffs, but as you can see, they do not affect operation at all.
(4 Scales + directions)
Front – Profit mark up , Unit Cost, Profit Margin %, Discount %
Back – Blank
Stock: 1
USD $59
6″/5″ Pocket USAF Aerial Photo Slide Rule
BRAND NEW, BOXED SET with the primo Pickett oxblood leather clip case with a data factor rear insert, sleeve box and manual. Very powerful compact rule with 16 scales!
Yes, we KNOW you don’t have a lot of aerial pictures to scale, but the flip side is a great Pocket Trig rule, similar to the N200!
Traditional White (T), black scales, including folded and inverted scales, plus trig scales, all aluminum construction. Don’t miss your chance to get one of these unusual pocket rules, they are an excellent design, and very useful in the pocket sized format with the built in data table.
(16 Scales!)
Front – L, A, DF, [ CF, CIF, T, S, C, ] D, DI, K
Back – Ground Size, Ground Speed, [ Image Size cm, inch, Focal length, ] Altitude
Stock: 55
USD $89
6″/5″ Pocket Slide Rule
These are new, N200-T Pocket Duplex Rule boxed sets, all rules are in their original factory packaging, including the original plastic bag around the rule – as a result, some of the rules show minor discoloration. Aluminum/magnesium bodies in EyeSaver (ES) yellow, black scales, black leather case with gold embossed logo.
(12 Scales)
Front – K, A, [ B, CI, C, ] D, L
Back – [ S, ST, T, C, ] D
Stock: 7
USD $89
6″/5″ Pocket Slide Rule
These are new, N200-T Pocket Duplex Rule boxed sets, all rules are in their original factory packaging, including the original plastic bag around the rule – as a result, some of the rules show minor discoloration. Aluminum/magnesium bodies, black scales, black leather case with gold embossed logo.
(12 Scales)
Front – K, A, [ B, CI, C, ] D, L
Back – [ S, ST, T, C, ] D
Stock: 10
USD $33
12″ / 10″ Simplex Slide Rule
This is something of a franken-rule, featuring the body from a Pickett 120-T, and the slide from a Pickett 120-ES, giving the rule improved readability. Embossed plastic construction, with black scales. A good student or starter rule, includes the original fibreboard case.
(9 Scales)
Front – K, A, [ B, S, T, CI, C ] D, L
Stock: 1
USD $44
12″/10″ Scholar Slide Rule
NEW factory boxed sets, with black leatherette case. This rule is a step up from the 120 model, featuring additional scales and conversion factors on the back of the rule. Perfect for students. Rules are in new/mint condition, boxes show signs of wear.
(12 Scales)
Front – K, A, [ B, CI, C, ] D, L
Back – [ S, ST, T, C ] D
Stock: 4
USD $39
12″ / 10″ Simplex Slide Rule
New in its original box, and includes black leatherette case, and instructions. Embossed white plastic construction, with black scales. A good student or starter rule.
(9 Scales)
Front – K, A, [ B, S, T, CI, C ] D, L
Stock: 1
USD $33
2″ / 10″ Simplex Slide Rule
Comes with original black leatherette case. Embossed white plastic construction (“T” for traditional body), black scales. A good student or starter rule. These rules are in near new condition.
(9 Scales)
Front – K, A, [ B, S, T, CI, C ] D, L
Stock: 8
USD $33
12″ / 10″ Simplex Slide Rule
In good condition with minor marking, comes with original leatherette case. Embossed yellow (ES eye-saver) plastic construction, black scales. A very useful student rule.
(9 Scales)
Front – K, A, [ B, S, T, CI, C ] D, L
Stock: 2
USD $33
12″ / 10″ Simplex Slide Rule
Comes with original brown leatherette case. Embossed white plastic construction, black scales, and grey plastic end braces. A good student or starter rule. This is a slightly slimmer version of the Microline 120 rule.
(9 Scales)
Front – K, A, [ B, T, S, CI, C ] D, L
Stock: 1
USD $44
12″ / 10″ Microline Simplex Trig Slide Rule w/Conversion Data
New bagged sets, with leatherette case, and factory instruction sheet. Embossed white plastic construction, black scales. A very useful student rule with conversion factors on the reverse side. These were shrink-wrapped hanging cards, some of these have been re-bagged due to failure in the original blisterpack plastic.
(9 Scales)
Front – K, A, [ B, S, T, CI, C ] D, L
Back – Conversion Factors
Stock: 5
USD $39
12″ / 10″ Simplex Slide Rule
Comes with original instruction sheet and leatherette case in a blister pack. Embossed white plastic construction, black scales. A very useful student rule, and an ideal first slide rule gift! These are MINT condition, perfect. You can give this to very young kids, as it can be easily washed in a sink with a bit of dish detergent if it gets covered in PB+J.
(9 Scales)
Front – K, A, [ B, S, T, CI, C ] D, L
Stock: 2
USD $159
12″ / 10″ Electronic Duplex Slide Rule
New / mint condition rule with maroon leather case, gold embossed with Cleveland Institute of Electronics and Pickett logo. Traditional (T) white coated aluminum construction, black and red scales, optimized for electronics problems. Includes belt loop strap, and manual reprint.
This is an extremely useful rule, made in the trademark aluminum body format by Pickett. Fortunately, all the special scales are SELF-DOCUMENTING on the right hand side, unusual for Pickett!
(15 Scales)
Front – H, 2pi, A, [ B, S, T, CI, C ] D, L, Ln
Back – Reactance/Resonance Decimal Point locator scales formulas and factors
Stock: 23
USD $149
12″ / 10″ Electronic Duplex Slide Rule
New / mint condition rule with maroon leather case, gold embossed with Cleveland Institute of Electronics and Pickett logo. Traditional (T) white coated aluminum construction, black and red scales, optimized for electronics problems.
This is an extremely useful rule, made in the trademark aluminum body format by Pickett. Fortunately, all the special scales are SELF-DOCUMENTING on the right hand side, unusual for Pickett!
(15 Scales)
Front – H, 2pi, A, [ B, S, T, CI, C ] D, L, Ln
Back – Reactance/Resonance Decimal Point locator scales formulas and factors
Stock: 1
USD $80
12″/10″ Full Size Simplex Math Slide Rule
This rule exists in two formats, and later ones came without the special rear scales, and just a trig manual. An excellent student rule with the unusual ability to ADD and SUBTRACT, and do 20 decade calculations.
(10 Scales)
Front – A, [ B, CI, C, ] D, L
Back – X, [ Y, C* ] D*
Stock: 1
USD $86
12″/10″ Full Size Simplex Math Slide Rule
This rule exists in two formats, and later ones came without the special rear scales, and just a trig manual. An excellent student rule with the unusual ability to ADD and SUBTRACT, and do 20 decade calculations.
(10 Scales)
Front – A, [ B, CI, C, ] D, L
Back – X, [ Y, C* ] D*
Stock: 1
USD $95
12″/10″ Full Size Simplex Math Slide Rule, Boxed Set complete with box, case, manual, and warranty card!
ES (Eye-Saver) Yellow aluminum construction. Very high quality, American Made, Pickett rule. This rule exists in two formats, and later ones came without the special rear scales, and just a trig manual. An excellent student rule with the unusual ability to ADD and SUBTRACT, and do 20 decade calculations. Boxes have carton creases, storage scuffs, tears and marks. Can ADD, SUBTRACT and do 20 decade Multiplication/Division
(10 Scales)
Front – A, [ B, CI, C, ] D, L
Back – X, [ Y, C* ] D*
Stock: 3
USD $149
12″ / 10″ Hi Log Log Duplex Slide Rule
Eye-saver yellow (ES) coated aluminum construction, black and red scales. This is a very sophisticated Log Log rule, made in the trademark aluminum body format by Pickett. Comes with original Pickett box, embossed brown leather case, and manual.
(22 Scales)
Front – LL2+0.1, LL2-0.1, DF [ CF, CIF, L, CI, C ] D, LL3+1.0, LL3-1.0
Back – LL1+0.01, LL1-0.01, A, [ B, T, ST, S, C ] D, DI, K
Stock: 1
USD $129
12″ / 10″ Power Trig Slide Rule
Very nice trig rule with black and red (inverse) scales, on the white (Traditional) body. This has the split square root scales, S, T and ST, plus DI scale for more calculating power and precision. Includes black textured leather case with gold embossed Pickett logo, manual, and original box w/warranty card. NIB, mint condition.
(17 Scales)
Front – K, A, [ B, ST, T, S, C ], D, DI
Back – L, DF, [ CF, CIF, CI, C ], D, DI
Stock: 2
USD $115
12″ / 10″ Capitol Radio Engineering Institute Log-Log Slide Rule
Very nice engineering rule with black and red (inverse) scales, on the yellow (Eye Saver) body, made for CREI. Comes in its original box, and includes brown textured leatherette case, manual, and original box w/warranty card. NIB, mint condition.
(16 Scales)
Front – K, A, [ B, CI, C ], D, L, Ln
Back – LL2, LL1, [ S, ST, T, C], D, LL3
Stock: 1
USD $44
2″ / 10″ Microline Simplex Trig Slide Rule w/Conversion Data
In its original “5 Moon Landings” box, and leatherette case. Embossed white plastic construction, black scales. A very useful student rule with conversion factors on the reverse side.
(9 Scales)
Front – K, A, [ B, S, T, CI, C ] D, L
Back – Conversion Factors
Stock: 1
USD $129
12″ / 10″ Power Trig Slide Rule
Very nice trig rule with black and red (inverse) scales, on the green(Eye Saver, very rare) body. This has the split square root scales, S, T and ST, plus DI scale for more calculating power and precision. Includes black textured leather case with gold embossed Pickett logo, manual, and original box w/warranty card. NIB, mint condition.
(17 Scales)
Front – K, A, [ B, ST, T, S, C ], D, DI
Back – L, DF, [ CF, CIF, CI, C ], D, DI
Stock: 1
USD $95
12″ / 10″ Power Trig Slide Rule
Very nice trig rule with black and red (inverse) scales, on the green(Eye Saver, very rare) body. This has the split square root scales, S, T and ST, plus DI scale for more calculating power and precision. Includes black textured leather case with gold embossed Pickett logo, manual, and original box. Case, manual, and box have signs of wear and are in fair condition, rule is good condition.
(17 Scales)
Front – K, A, [ B, ST, T, S, C ], D, DI
Back – L, DF, [ CF, CIF, CI, C ], D, DI
Stock: 1
USD $129
12″ / 10″ Power Trig Slide Rule
Very nice trig rule with black and red (inverse) scales, on the yellow (Eye Saver) body. This has the split square root scales, S, T and ST, plus DI scale for more calculating power and precision. Includes black textured leather case with gold embossed Pickett logo, manual, and original box w/warranty certificate.
(17 Scales)
Front – K, A, [ B, ST, T, S, C ], D, DI
Back – L, DF, [ CF, CIF, CI, C ], D, DI
Stock: 5
USD $95
12″ / 10″ Electronic Duplex Slide Rule
New and in the original factory plastic, the this 531 is an all aluminum rule in Pickett’s Eye Saver (ES) yellow, featuring black scales. This specific rule was made for the Capitol Radio Engineering Institute.
(17 Scales)
Front – L, Ln, A, [B, CI, C], D, 2π, K
Back – LL2, LL1, [S, ST, T, C], D, LL3
Stock: 1
USD $129
A practical, all aluminum, pocket commerce rule, new and in its factory plastic. Features calculation guide and specialized scales on the reverse side of the rule for performing ownership and cost calculations.
Provided with a Sphere Research leather clip case.
(12 Scales)
Front – K, A, [ B, CI, C ], D, L
Back – R, [ C, S, A], Q
Stock: 1
USD $59
This is an unusual rule, with not many good examples circulating. It is a very basic nine scale rule that was most often used for promotional purposes, with all aluminum construction and a slide that is nearly the full width of the rule.
(9 Scales)
Front – K, A, B, T, S, CI, C, D, L
Back – Blank, promotional logo
Stock: 1
USD $95
6″/5″ Pocket Log Log Speed Slide Rule
Pocket Duplex Log Log Speed Rule, Pickett’s most powerful compact rule with an amazing 22 scales, black and red scales, aluminum construction! These are used rules that come in a variety of different leather cases, with either a pull tab or clip case.
(22 Scales!)
Front – LL1+, LL1-, A, [ B, ST, T, S, C, ] D, DI, K
Back – LL2+, LL2-, DF, [ CF, Ln, L, CI, C, ] D, LL3+, LL3-
Stock: 6
USD $105
6″ / 5″ Trig Slide Rule
Very nice trig rule with black and red (inverse) scales, on the white T (traditional) body. This has the split square root scales, S, T and ST, plus DI scale for more calculating power and precision. A very nice rule for general use.
Includes original leather case, either with pull tab or clip case.
(16 Scales)
Front – K, A, [ B, ST, T, S, C ], D, DI
Back – DF, [ CF, CIF, CI, C ], D, L
Stock: 5
USD $69
6″/5″ Pocket Slide Rule
Pocket Duplex Rule, aluminum/magnesium bodies, some rules have promotional logos. Includes original leather cases, some with pull tabs, clips, or slip cases.
These rules and cases are in fair condition.
(12 Scales)
Front – K, A, [ B, CI, C, ] D, L
Back – [ S, ST, T, C, ] D
Stock: 10
USD $149
6″/5″ Pocket Slide Rule
New in box with original leather case (pull tab style with clip), pocket Business Duplex Rule. Eye Saver yellow (ES) aluminum construction with red and black scale markings.
(14 Scales)
Front – K, A, [ B, CI, C, ] D, L
Back – R%, DF, [ CF R%, C, ] D, C%
Stock: 1
USD $189
12″ / 10″ Electronic Duplex Slide Rule
In excellent condition with suede case. Eye Saver yellow (ES) coated aluminum construction, black and red scales, optimized for electronics problems, with dual marking on the front, and Chan Street special multi-decade electronics scales on the rear (Like the N16!).
This is an extremely useful rule, made in the trademark aluminum body format by Pickett.
(16 Multi-function Scales)
Front – L, Ln, Cr/AI, [ Lr/B, ST, T, C/L/I/C, ] F/X/E/R/W/D, Xc/DI, K
Back – Reactance/Resonance Decimal Point locator scales formulas and factors
Stock: 1
USD $75
12″/10″ Full Size Simplex Math Slide Rule
This rule exists in two formats, and later ones came without the special rear scales, and just a trig manual. An excellent student rule with the unusual ability to ADD and SUBTRACT, and do 20 decade calculations.
(10 Scales)
Front – A, [ B, CI, C, ] D, L
Back – X, [ Y, C* ] D*
Stock: 1
USD $69
Pickett’s Best Self-Teaching Rule!
12″/10″ Full Size Simplex Trig Slide Rule, T (traditional) white construction. Very high quality, American Made, Pickett rule – a great instructional rule that never loses its manual (it’s imprinted on the back surface!) at a great price. An excellent student rule with good trig capability.
Front – K, A, [ B, T, S, CI, C, ] D, L
Back – instructions, fractional/decimal equivalents
Stock: 1
USD $75
A specialised, full size, all metal rule made by Pickett for Fisher Controls.
Front -ΔP Liquid Pressure Drop, %Q C2, P1 Inlet Pressure, Flow, Q, Liquid Cv, Gas or Vapor Cg
Back – PSI Drop, P1, Gas Specific Gravity, Temp, Superheat, Flow, F, Cg Gas, Cs Steam,
Stock: 1
USD $139
12″ / 10″ Hi Log Log Duplex Slide Rule
Late model with black leather case. Traditional (T) white coated aluminum construction, black and red scales. This is a very sophisticated rule, made in the trademark aluminum body format by Pickett.
(22 Scales)
Front – LL2+0.1, LL2-0.1, DF [ CF, CIF, L, CI, C ] D, LL3+1.0, LL3-1.0
Back – LL1+0.01, LL1-0.01, A, [ B, T, ST, S, C ] D, DI, K
Stock: 2
USD $89
Pocket Duplex Rule, complete in factory box with embossed leather pocket case with nifty extractor tab to easily pull the rule out, and Pickett instruction manual.
(12 Scales)
Front – K, A, [ B, CI, C, ] D, L
Back – [ S, ST, T, C, ] D
Stock: 2
USD $129
12″/10″ Full Size Duplex Trig Slide Rule
Includes special multi-decade expanded scales, capable of an astonishing 20-60 decades of dynamic range.
Eye Saver yellow aluminum construction with black and red contrasting scales, very high quality, American Made, Pickett rule. A very useful rule, ideal for many engineering tasks.
(18 Scales)
Front – K, A, [ B, T, S, CI, C, ] D, L
Back – K*, A*, [ B*, T*, S*, CI*, C*, ] D*, L*
Stock: 1
USD $85
12″/10″ Full Size Simplex Trig Slide Rule
This isa self-teaching rule, with extensive directions on the reverse side.
T (Traditional) White aluminum construction. Very high quality, American Made, Pickett rule. An excellent student rule with good trig capability, includes the original box, leather case, and instruction manual.
(9 Scales)
Front – K, A, [ B, T, S, CI, C, ] D, L
Back – instructions, fractional/decimal equivalents
Stock: 2
USD $95
12″ / 10″ Trig Slide Rule
Very nice trig rule with black and red (inverse) scales, on the yellow (Eye Saver) body. This has the split square root scales, S, T and ST, plus DI scale for more calculating power and precision. Includes black textured leather case with gold embossed Pickett logo.
(17 Scales)
Front – K, A, [ B, ST, T, S, C ], D, DI
Back – L, DF, [ CF, CIF, CI, C ], D, DI
Stock: 4
USD $159
12″ / 10″ Dual Base Log Log Speed Slide Rule
Includes original user manual and leather case. in black or tan. Dual log scale design with repeated C/D scales and DI scale for ease and speed of use.
This is a very sophisticated Log Log rule, made in the trademark adjustable aluminum body format by Pickett, an enhanced N500/800 design with added scale features.
Note that the full Pickett teacher’s manual is now on line in Adobe Acrobat PDF format HERE for you FREE!
(28 Scales)
Front – LL0-0.001, LL0+0.001, LL1+0.01, LL1-0.01, DF, [ CF, CIF, L, CI, C ], D, LL2+0.1, LL2-0.1, LL3+1.0, LL3-1.0
Back – Sq Rt1, Sq Rt2, K, A, [ B, ST, T, CI, S, C ], D, DI, DFm
Stock: 3
USD $139
12″ / 10″ Hi Log Log Duplex Slide Rule
Eye-saver yellow (ES) coated aluminum construction, black and red scales. This is a very sophisticated Log Log rule, made in the trademark aluminum body format by Pickett. Comes with original Pickett leather case.
Note that the full Pickett teacher’s manual is now on line in Adobe Acrobat PDF format HERE for you FREE!
(22 Scales)
Front – LL2+0.1, LL2-0.1, DF [ CF, CIF, L, CI, C ] D, LL3+1.0, LL3-1.0
Back – LL1+0.01, LL1-0.01, A, [ B, T, ST, S, C ] D, DI, K
Stock: 4
USD $129
One of Pickett’s more advanced rules, this 22 scale, aluminum body rule comes in Eye-saver yellow (ES), with black and red scales. This is a very sophisticated Log Log rule, made in the trademark aluminum body format by Pickett. The original case on this rule has some wear and damage, but does come with the belt loop accessory.
Scales include:
Front – LL2+0.1, LL2-0.1, DF [ CF, CIF, L, CI, C ] D, LL3+1.0, LL3-1.0
Back – LL1+0.01, LL1-0.01, A, [ B, T, ST, S, C ] D, DI, K
Stock: 1
USD $175
This is a very sophisticated 34 scale rule, made in the trademark aluminum body format by Pickett, an extremely powerful but somewhat crowded rule. Has hyperbolic scales, expanded trig, square and cube root scales, DI and two types of folded scales. Comes with the original brown leather case.
Scales include:
Front – LL1+.000, LL1-.000, LL2+.00, LL2-.00, DF/m, [ CF/m, TH, SH, SH, L, CI, C, ] LL3+.0, LL3-.0, LL4+0., LL4-0.
Back – 3 cube root scales, DF [ CF, CIF, T, T, ST, S, CI, C, ] D, DI, 2 square root scales
Stock: 2
USD $69
ES (Eye-Saver) Yellow aluminum construction, high-quality American made, Pickett rule. An excellent student rule with good trig capability, that never loses its instruction manual (it’s printed on the back).
Scales include:
Front – K, A, [ B, T, S, CI, C, ] D, L
Back – instructions, fractional/decimal equivalents
Stock: 13
USD $15
Provided in the most seductive of all box colors (blue), is this Pickett drafting set. In addition to the compass, it also includes extra leads, a sharpener, and drafting pencil.
Stock: 1
USD $85
This all-metal 23-scale rule has some unique features. The reverse side of the rule features a split scale, with instructions outlined in the centre of the rule, and positive values read on the left end of the scale, and negative values on the right.
Scales are as follows:
Front – ^-3, ^-3, ^-3, L, T, T, ST< S, CI, C, D, ^-2, ^-2
Back – C, D, T’, T’, ST’, S’, DN, RN-DZ, ^-2, ^-3
Stock: 1
Sphere Research Corporation