The bronzes of manganese, tin, and zinc were perhaps the first upon which important investigations were made; they were obtained by adding to an alloy of copper, zinc, and tin (ordinary bronze) a definite quantity of the cupro-manganese of the type indicated above (Cu 70, Mn 30).  By this means the resistance is increased fully nine per cent., probably in the same way as the copper, that is, by the deoxidizing effect of the manganese, as both the copper and the tin are always more or less oxidized in ordinary bronzes.

Manganese combines with tin just the same as it does with copper, and the proportion which is recommended as giving the highest resistances is three to six per cent. of cupro-manganese.

However, notwithstanding the use of cupro-manganese, the tin, as in ordinary bronzes, has a tendency to liquate in those portions of the mould which are the hottest, and which become solid the last, especially in the case of moulds having a great width.

From a series of experiments made at Isabelle Huette, it has been found that the metal which has the greatest resisting qualities was obtained from

Copper......................85.00
Manganese................... 6.00
Zinc........................ 5.00

5 per cent. of cupro-manganese = manganese 1.00 remaining in the metal.

The best method of procedure is first to melt the copper in a crucible, and then to add the tin and the zinc; finally the cupro-manganese is added just at the moment of pouring, as in the Manhes process; then the reaction on the oxides is very effective, there is a boiling with scintillation similar to the action produced in the Bessemer and Martin process when ferro-manganese is added to the bath of steel.

The following are some of the results obtained from thirteen alloys obtained in this manner.  These samples were taken direct from the casting and were tested with the machine at Friedrich-Wilhelms-huette, and with the one at the shops of the Rhine Railroad.  Their resistance was considerably increased, as with the other alloys, by rolling or hammering.

-------+------+------+-----+---------+---------+-------

---+--------+-------+
|      |      |     |         |         |          | Weight |       |
|      |      |     |         |         |Limit of  |  of    | Elong-|
|Nature|      |     |         |         |elasticity|fracture| ation,|
|  of  |      |     |         |  Cupro- |in kilos  |in kilos|  per- |
Numbers|mould.|Copper| Tin.|  Zinc.  |manganese|per mm.   | per mm.|centage|
-------+------+------+-----+---------+---------+----------+-

-------+-------+
1   | Sand | 85.00| 6.00|   5.00  |         |   11.30  |  16.00 |   --  |
2   |  --  | 85.00| 6.00|   5.00  |   4.00  |   13.00  |  16.10 |  2.00 |
3   | Cast.| 87.00| 8.70|   4.30  |   4.00  |     --   |  19.40 |   --  |
4   |  --  | 85.00| 6.90|   5.00  |   6.00  |     --   |  18.80 |  6.00 |
5   |  --  | 85.00| 6.00|   5.00  |   6.00  |     --   |  19.75 |  7.00 |