Group heroism was no less remarkable. For the flooding of the powder magazine in the naval yard an entire battery volunteered. This was why the second explosion did not actually occur. Freight handlers too, as well as soldiers, revealed themselves possessors of the great spirit. A conspicuous case was that of the longshoremen working on board of a ship laden with explosives. Fully realizing the impending danger, because of the nearness of the burning munitioner, they used what precious minutes of life remained them to protect their own ship's explosives from ignition. A fire did afterwards start upon the ship but a brave captain loosed her from the pier, and himself extinguished the blaze which might soon have repeated in part the devastations already wrought. No disaster psychology should omit a discussion of the psychology of helpfulness--that self-help to which the best relief workers always appeal, as well as of the mutual aid upon which emergency relief must largely depend. Mutual aid while not a primary social fact is inherent in the association of members of society, as it also "obtains among cells and organs of the vital organism." As it insured survival in the earlier stages of evolution[85] so it reveals itself when survival is again threatened by catastrophe. [85] Kropotkin, Prince, _Mutual Aid_ (N. Y., 1919), ch. i, p. 14. The illustrations of mutual aid at Halifax would fill a volume. Not only was it evidenced in the instances of families and friends but also in the realm of business. Cafes served lunches without charge. Drug stores gave out freely of their supplies. Firms released their clerks to swell the army of relief. A noteworthy case of community service was that of the Grocers' Guild announcing that its members would fill no orders for outside points during the crisis, that they would cooperate with the relief committee in delivering foodstuffs free of charge to any point in the city, and that their stocks were at the disposal of the committee at the actual cost to them.[86] By incidents such as these, Halifax gained the appellation of the City of Comrades. [86] Johnstone, _op. cit._