IX. NAVAL ARCHITECTURE, ETC. 487 



2144g. Skew Mitres. 



The Committee, Royal Museum, Peel Park, Salford. 

 A pair of toothed mitre wheels mounted on shafts that cross each other. 

 The invention of the late R, Roberts, C.E., of Manchester, 1836. 



2144h. Intermittent Wheels. 



The Committee, Royal Museum, Peel Park, Salford. 

 The larger wheel performs six revolutions for one of the lesser. The 

 invention of the late R. Roberts, C.E., of Manchester. 



2145. Model of Cugnot's Steam Carriage, 1783.^ 



Conservatoire des Arts et Metiers, Paris. 



2146. Model of a centrifugal smoke purifier. 



Dr. Otto Braun, Berlin, 



This model shows the action of centrifugal force on bodies suspended in 

 gases, by means of it -sparks, soot, tar, ammonia, &c. can be removed from 

 smoke. 



2146a. TyndalPs Smoke Filter Respirator, suitable for 

 firemen, fire-escape men, and for persons entering deleterious 

 atmospheres. James Sinclair. 



The filtration is by means of layers of dry cotton wool, cotton wool 

 dipped in glycerine, and charcoal. 



2146b. TyndalPs Smoke Filter Respirator, combined 

 with elastic tube, suitable for mining operations, chemical works, 

 breweries, &c. James Sinclair. 



This respirator is designed to enable the wearer to enter and breathe freely 

 in mephitic gases by means of the tube, which can be used in lengths up to 

 90 feet, the wearer being enabled to communicate verbally with those out- 

 side and they with him. 



1925. Chinese Steel Helmets (2). 



Bennet Woodcraft, F.R.S. 



1926. Chinese Cane Helmets (2). 



Bennet Woodcroft, F.R.S. 



IX. SHIPPING, NAVAL ARCHITECTURE, AND 

 MARINE ENGINEERING. 



2147. Models made of hard paraffin for ascertaining the 

 Resistance of Ships by measuring the resistance of their models. 



W. Froude, F.R.S. 



The models, from 6 to 16 feet in length, and from 120 Ibs. to 700 Ibs. dis- 

 placement, are made of hard paraffin. The experimental apparatus em- 

 ployed in the treatment of the models includes appliances for designing, 

 moulding, and casting them, shaping them by automatic machinery, moving 



