II. CALCULATING MACHINES.' 5 



17. Kentish's Compound Slide Rule. 



Dring and Page. 



This is a new and ingenious arrangement of Gunter's lines, by means of 

 which problems in trigonometry and navigation can be solved, in addition to 

 those ordinarily done on the slide rule. 



17 a. Dr. Roget's Slide Rule of Involution. 



W. H. Prosser. 



This rule exhibits at one view all the powers and roots of any given number. 

 It is a measure of the powers of numbers, in the same way as Gunter's scale 

 is a measure of their ratios. Described in Phil. Trans. 1815, Part 1. 



17b. Slide Rules (3), with double sliders, being suggested 

 improvements on the ordinary slide rule, giving greater clearness 

 in reading off, and avoiding complication in the lines. 



W. H. Prosser. 



17c. Glass Slide Rule, invented by Leon Lalanne. 



W. FT. Prosser. 



This rule is made of two slips of card, upon which the scales are printed. 

 The slider, also made of card, has scales, constants, and gauge points printed 

 on both sides, and moves between the two slips. The whole is enclosed 

 between two pieces of glass. 



17d. Slide Rule, with only one slider, adapted for the pocket- 

 book. Arranged by J. W. Woollgar. W. H. Prosser. 



18. Sailer on's Slide Rule for reduction of volumes of gases 

 to standard temperature and pressure. 



The Council of the Yorkshire College of Science. 



19. Sailer on's Slide Rule for reducing barometric heights 

 to standard temperature. 



The Council of the Yorkshire College of Science. 



II. CALCULATING MACHINES. 



20. Calculating Machine, adapted to trigonometrical 

 computations, invented by Sir Samuel Morland (1625-1695), and 

 constructed by Henry Sutton and Samuel Knibbs of London, in 

 1664. Formerly belonging to Mr. C. Babbage, F.R.S. 



Major- General Babbage. 



On the lid of this machine is the following inscription : 



" Machina Cyclologica Trigonometrice Qu& Tribus datis, reliqua omnia in 

 Triangulis Planis Quaesita faciliter atque unico intuitu expediuntur a Samuele 

 Morlando inventa Anno Salutis MDCLXIII. 



